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Scuba diver with air tank clearly visible

Scuba diving ("scuba" originally being an acronym for Self Contained Underwater Breathing Apparatus, although now widely considered a word in its own right)[1] is a form of underwater diving in which a diver uses a scuba set to breathe underwater for recreation, commercial or industrial reasons.[2]

Unlike early diving, which relied exclusively on air pumped from the surface, scuba divers carry their own source of breathing gas (usually compressed air),[3] allowing them greater freedom than with an air line. Both surface supplied and scuba diving allow divers to stay underwater significantly longer than with breath-holding techniques as used in snorkelling and free-diving.

According to the purpose of the dive, a diver usually moves underwater by swimfins attached to the feet, but external propulsion can come from an underwater vehicle, or a sled pulled from the surface.

Contents

History

Original Aqualung SCUBA set

The first commercially successful scuba sets were the Aqualung open-circuit units developed by Emile Gagnan and Jacques-Yves Cousteau, in which compressed gas (usually air) is inhaled from a tank and then exhaled into the water, and the descendants of these systems are still the most popular units today.

The open circuit systems were developed after Cousteau had a number of incidents of oxygen toxicity using a rebreather system, in which exhaled air is reprocessed to remove carbon dioxide. Modern versions of rebreather systems (both semi-closed circuit and closed circuit) are still available today, and form the second main type of scuba unit, most commonly used for technical diving, such as deep diving.

Etymology

The term SCUBA (an acronym for Self-Contained Underwater Breathing Apparatus) arose during World War II, and originally referred to United States combat frogmen's oxygen rebreathers, developed by Dr. Christian Lambertsen for underwater warfare.[3][4][5]

The word SCUBA began as an acronym, but it is now usually thought of as a regular word—scuba. It has become acceptable to refer to "scuba equipment" or "scuba apparatus"—examples of the linguistic RAS syndrome.

Types of diving

Professional diver performing underwater welding

Scuba diving may be performed for a number of reasons, both personal and professional. Most people begin though recreational diving, which is performed purely for enjoyment and has a number of distinct technical disciplines to increase interest underwater, such as cave diving, wreck diving, ice diving and deep diving.

Divers may be employed professionally to perform tasks underwater. Most of these commercial divers are employed to perform tasks related to the running of a business involving deep water, including civil engineering tasks such as in oil exploration, underwater welding or offshore construction. Commercial divers may also be employed to perform tasks specifically related to marine activities, such as naval diving, including the repair and inspection of boats and ships, salvage of wrecks or underwater fishing, like spear fishing.

Other specialist areas of diving include military diving, with a long history of military frogmen in various roles. They can perform roles including direct combat, infiltration behind enemy lines, placing mines or using a manned torpedo, bomb disposal or engineering operations. In civilian operations, many police forces operate police diving teams to perform search and recovery or search and rescue operations and to assist with the detection of crime which may involve bodies of water. In some cases diver rescue teams may also be part of a fire department or lifeguard unit.

Lastly, there are professional divers involved with the water itself, such as underwater photography or underwater filming divers, who set out to document the underwater world, or scientific diving, including marine biology and underwater archaeology.

Reasons for diving may include:

Type of diving Classification
aquarium maintenance in large public aquariums commercial, scientific
boat and ship inspection, cleaning and maintenance commercial, naval
cave diving technical, recreational
civil engineering in harbors, water supply, and drainage systems commercial
crude oil industry and other offshore construction and maintenance commercial
demolition and salvage of ship wrecks commercial, naval
diver training for reward professional
fish farm maintenance commercial
fishing, e.g. for abalones, crabs, lobsters, pearls, scallops, sea crayfish, sponges commercial
frogman, manned torpedo military
harbor clearance and maintenance commercial, military
media diving: making television programs, etc. professional
mine clearance and bomb disposal, disposing of unexploded ordnance military, naval
pleasure, leisure, sport recreational
underwater photography professional, recreational
policing: diving to investigate or arrest unauthorized divers police diving, military, naval
search and recovery diving commercial
search and rescue diving police
spear fishing professional (occasionally), recreational
stealthy infiltration military
marine biology scientific, recreational
underwater tourism recreational
underwater archaeology (shipwrecks; harbors, and buildings) scientific, recreational
underwater welding commercial

Breathing underwater

Scuba diver on reef

Water normally contains dissolved oxygen from which fish and other aquatic animals extract all their required oxygen as the water flows past their gills. Humans lack gills and do not otherwise have the capacity to breathe underwater unaided by external devices.[3] Although the feasibility of filling and artificially ventilating the lungs with a dedicated liquid (Liquid breathing) has been established for some time,[6] the size and complexity of the equipment allows only for medical applications with current technology.[7]

Early diving experimenters quickly discovered it is not enough simply to supply air in order to breathe comfortably underwater. As one descends, in addition to the normal atmospheric pressure, water exerts increasing pressure on the chest and lungs—approximately 1 bar or 14.7 psi for every 33 feet or 10 meters of depth—so the pressure of the inhaled breath must almost exactly counter the surrounding or ambient pressure to inflate the lungs. It generally becomes difficult to breathe through a tube past three feet under the water.[3]

By always providing the breathing gas at ambient pressure, modern demand valve regulators ensure the diver can inhale and exhale naturally and virtually effortlessly, regardless of depth.

Because the diver's nose and eyes are covered by a diving mask; the diver cannot breathe in through the nose, except when wearing a full face diving mask. However, inhaling from a regulator's mouthpiece becomes second nature very quickly.

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Open-circuit

The most commonly used scuba set today is the "single-hose" open circuit 2-stage diving regulator, coupled to a single pressurized gas cylinder, with the first stage on the cylinder and the second stage at the mouthpiece.[2] This arrangement differs from Emile Gagnan's and Jacques Cousteau's original 1942 "twin-hose" design, known as the Aqua-lung, in which the cylinder's pressure was reduced to ambient pressure in one or two or three stages which were all on the cylinder. The "single-hose" system has significant advantages over the original system.

In the "single-hose" two-stage design, the first stage regulator reduces the cylinder pressure of about 200 bar (3000 psi) to an intermediate level of about 10 bar (145 psi) The second stage demand valve regulator, connected via a low pressure hose to the first stage, delivers the breathing gas at the correct ambient pressure to the diver's mouth and lungs. The diver's exhaled gases are exhausted directly to the environment as waste. The first stage typically has at least one outlet delivering breathing gas at unreduced tank pressure. This is connected to the diver's pressure gauge or computer, in order to show how much breathing gas remains.

Rebreather

An Inspiration electronic fully closed circuit rebreather

Less common are closed and semi-closed rebreathers,[8] which unlike open-circuit sets that vent off all exhaled gases, reprocess each exhaled breath for re-use by removing the carbon dioxide buildup and replacing the oxygen used by the diver.

Rebreathers release few or no gas bubbles into the water, and use much less oxygen per hour because exhaled oxygen is recovered; this has advantages for research, military[2], photography, and other applications. The first modern rebreather was the MK-19 that was developed at S-Tron by Ralph Osterhout that was the first electronic system.[citation needed] Rebreathers are more complex and more expensive than sport open-circuit scuba, and need special training and maintenance to be safely used.[8]

Because the nitrogen in the system is kept to a minimum, decompressing is much less complicated than traditional open-circuit scuba systems and, as a result, divers can stay down longer. Because rebreathers produce very few bubbles, they do not disturb marine life or make a diver’s presence known; this is useful for underwater photography, and for covert work.

Gas mixtures

EANxDecal.png
Nitrox cylinder marked up for use

For some diving, gas mixtures other than normal atmospheric air (21% oxygen, 78% nitrogen, 1% trace gases) can be used,[2][3] so long as the diver is properly trained in their use. The most commonly used mixture is Enriched Air Nitrox, which is air with extra oxygen, often with 32% or 36% oxygen, and thus less nitrogen, reducing the likelihood of decompression sickness. The reduced nitrogen may also allow for no or less decompression stop times and a shorter surface interval between dives. A common misconception is that nitrox can reduce narcosis, but research has shown that oxygen is also narcotic.[9][10]

Several other common gas mixtures are in use, and all need specialized training. The increased oxygen levels in nitrox help fend off decompression sickness; however, below the maximum operating depth of the mixture, the increased partial pressure of oxygen can lead to oxygen toxicity. To displace nitrogen without the increased oxygen concentration, other diluents can be used, often helium, when the resultant mixture is called trimix.

For technical dives, some of the cylinders may contain different gas mixture for each phase of the dive, typically designated as Travel, Bottom, and Decompression. These different gas mixtures may be used to extend bottom time, reduce inert gas narcotic effects, and reduce decompression times.

Hazards and dangers

According to a 1970 North American study, diving was (on a man-hours based criteria) 96 times more dangerous than driving an automobile.[11] According to a 2000 Japanese study, every hour of recreational diving is 36 to 62 times riskier than automobile driving.[12]

Injuries due to changes in air pressure

Divers must avoid injuries caused by changes in air pressure. The weight of the water column above the diver causes an increase in air pressure in any compressible material (wetsuit, lungs, sinus) in proportion to depth, in the same way that atmospheric air causes a pressure of 101.3 kPa (14.7 pounds-force per square inch) at sea level. Pressure injuries are called barotrauma[3] and can be quite painful, in severe cases causing a ruptured eardrum or damage to the sinuses. To avoid them, the diver equalizes the pressure in all air spaces with the surrounding water pressure when changing depth. The middle ear and sinus are equalized using one or more of several techniques, which is referred to as clearing the ears.

The mask is equalized by periodically exhaling through the nose.

If a drysuit is worn, it too must be equalized by inflation and deflation, similar to a buoyancy compensator.

If properly equalized, the sinus passages can stand the increased pressure of the water with no problems. However, congestion due to cold, flu or allergies may impair the ability to equalize the pressure. This may result in permanent damage to the eardrum. Although there are many dangers involved in scuba diving, divers can decrease the dangers through proper training and education. Open-water certification programs highlight diving physiology, safe diving practices, and diving hazards.

Effects of breathing high pressure gas

Decompression sickness

The diver must avoid the formation of gas bubbles in the body, called decompression sickness[3] or 'the bends', by releasing the water pressure on the body slowly while ascending and allowing gases trapped in the bloodstream to gradually break solution and leave the body, called "off-gassing." This is done by making safety stops or decompression stops and ascending slowly using dive computers or decompression tables for guidance. Decompression sickness must be treated promptly, typically in a recompression chamber. Administering enriched-oxygen breathing gas or pure oxygen to a decompression sickness stricken diver on the surface is a good form of first aid for decompression sickness, although fatality or permanent disability may still occur.[13]

Nitrogen narcosis

Nitrogen narcosis or inert gas narcosis is a reversible alteration in consciousness producing a state similar to alcohol intoxication in divers who breathe high pressure gas at depth.[3] The mechanism is similar to that of nitrous oxide, or "laughing gas," administered as anesthesia. Being "narced" can impair judgment and make diving very dangerous. Narcosis starts to affect some divers at 66 feet (20 meters). At 66 feet (20 m), Narcosis manifests itself as slight giddiness. The effects increase drastically with the increase in depth. Almost all divers are able to notice the effects by 132 feet (40 meters). At these depths divers may feel euphoria, anxiety, loss of coordination and lack of concentration. At extreme depths, hallucinogenic reaction and tunnel vision can occur. Jacques Cousteau famously described it as the "rapture of the deep". Nitrogen narcosis occurs quickly and the symptoms typically disappear during the ascent, so that divers often fail to realize they were ever affected. It affects individual divers at varying depths and conditions, and can even vary from dive to dive under identical conditions. However, diving with trimix or heliox dramatically reduces the effects of inert gas narcosis.

Oxygen toxicity

Oxygen toxicity occurs when oxygen in the body exceeds a safe "partial pressure" (PPO2).[3] In extreme cases it affects the central nervous system and causes a seizure, which can result in the diver spitting out his regulator and drowning. Oxygen toxicity is preventable provided one never exceeds the established maximum depth of a given breathing gas. For deep dives (generally past 180 feet / 55 meters), divers use "hypoxic blends" containing a lower percentage of oxygen than atmospheric air. For more information, see Oxygen toxicity.

Refraction and underwater vision

A diver wearing an Ocean Reef full face mask

Water has a higher refractive index than air; it's similar to that of the cornea of the eye. Light entering the cornea from water is hardly refracted at all, leaving only the eye's crystalline lens to focus light. This leads to very severe hypermetropia. People with severe myopia, therefore, can see better underwater without a mask than normal-sighted people.

Diving masks and diving helmets and fullface masks solve this problem by creating an air space in front of the diver's eyes.[2] The refraction error created by the water is mostly corrected as the light travels from water to air through a flat lens, except that objects appear approximately 34% bigger and 25% closer in salt water than they actually are. Therefore total field-of-view is significantly reduced and eye-hand coordination must be adjusted.

(This affects underwater photography: a camera seeing through a flat window in its casing is affected the same as its user's eye seeing through a flat mask window, and so its user must focus for the apparent distance to target, not for the real distance.)

Divers who need corrective lenses to see clearly outside the water would normally need the same prescription while wearing a mask. Generic and custom corrective lenses are available for some two-window masks. Custom lenses can be bonded onto masks that have a single front window.

A "double-dome mask" has curved windows in an attempt to cure these faults, but this causes a refraction problem of its own.

Commando frogmen concerned about revealing their position when light reflects from the glass surface of their diving masks may instead use special contact lenses to see underwater.

As a diver descends, he must periodically exhale through his nose to equalize the internal pressure of the mask with that of the surrounding water. Swimming goggles are not suitable for diving because they only cover the eyes and thus do not allow for equalization. Failure to equalise the pressure inside the mask may lead to a form of barotrauma known as mask squeeze.[2][14]

Controlling buoyancy underwater

Diver under the Salt Pier in Bonaire.

To dive safely, divers must control their rate of descent and ascent in the water.[3] Ignoring other forces such as water currents and swimming, the diver's overall buoyancy determines whether he ascends or descends. Equipment such as the diving weighting systems, diving suits (Wet, Dry & Semi-dry suits are used depending on the water temperature) and buoyancy compensators can be used to adjust the overall buoyancy.[2] When divers want to remain at constant depth, they try to achieve neutral buoyancy. This minimizes gas consumption caused by swimming to maintain depth.

The downward force on the diver is the weight of the diver and his equipment minus the weight of the same volume of the liquid that he is displacing; if the result is negative, that force is upwards. Diving weighting systems can be used to reduce the diver's weight and cause an ascent in an emergency. Diving suits, mostly being made of compressible materials, shrink as the diver descends, and expand as the diver ascends, creating buoyancy changes. The diver can inject air into some diving suits to counteract the compression effect and squeeze. Buoyancy compensators allow easy and fine adjustments in the diver's overall volume and therefore buoyancy. For open circuit divers, changes in the diver's lung volume can be used to adjust buoyancy.

Avoiding losing body heat

Dry suit for reducing exposure

Water conducts heat from the diver 25 times[15] better than air, which can lead to hypothermia even in mild water temperatures.[3] Symptoms of hypothermia include impaired judgment and dexterity[16], which can quickly become deadly in an aquatic environment. In all but the warmest waters, divers need the thermal insulation provided by wetsuits or drysuits.[2]

In the case of a wetsuit, the suit is designed to minimize heat loss. Wetsuits are generally made of neoprene that has small gas cells, generally nitrogen, trapped in it during the manufacturing process. The poor thermal conductivity of this expanded cell neoprene means that wetsuits reduce loss of body heat by conduction to the surrounding water. The neoprene in this case acts as an insulator.

The second way in which wetsuits reduce heat loss is to trap a thin layer of water between the diver's skin and the insulating suit itself. Body heat then heats the trapped water. Provided the wetsuit is reasonably well-sealed at all openings (neck, wrists, legs), this reduces water flow over the surface of the skin, reducing loss of body heat by convection, and therefore keeps the diver warm (this is the principle employed in the use of a "Semi-Dry")

Spring suit and steamer

In the case of a drysuit, it does exactly that: keeps a diver dry. The suit is sealed so that frigid water cannot penetrate the suit. Drysuit undergarments are often worn under a drysuit as well, and help to keep layers of air inside the suit for better thermal insulation. Some divers carry an extra gas bottle dedicated to filling the dry suit. Usually this bottle contains argon gas, because of its better insulation as compared with air.[17]

Drysuits fall into two main categories neoprene and membrane; both systems have their good and bad points but generally their thermal properties can be reduced to:

  • Membrane: usually a trilaminate construction; owing to the thinness of the material (around 1 mm), these require an undersuit, usually of high insulation value if diving in cooler water.
  • Neoprene: a similar construction to wetsuits; these are often considerably thicker (7–8 mm) and have sufficient insulation to allow a lighter-weight undersuit (or none at all); however on deeper dives the neoprene can compress to as little as 2 mm thus losing a proportion of their insulation. Compressed or crushed neoprene may also be used (where the neoprene is pre-compressed to 2–3 mm) which avoids the variation of insulating properties with depth.

Avoiding skin cuts and grazes

Diving suits also help prevent the diver's skin being damaged by rough or sharp underwater objects, marine animals or coral.

Diving longer and deeper safely

There are a number of techniques to increase the diver's ability to dive deeper and longer:

Being mobile underwater

The diver needs to be mobile underwater. Streamlining dive gear will reduce drag and improve mobility. Personal mobility is enhanced by swimfins and Diver Propulsion Vehicles. Other equipment to improve mobility includes diving bells and diving shots.

Scuba dive training and certification agencies

Diving lessons in Monterey Bay, California

Recreational scuba diving does not have a centralized certifying or regulatory agency, and is mostly self regulated. There are, however, several large diving organizations that train and certify divers and dive instructors, and many diving related sales and rental outlets require proof of diver certification from one of these organizations prior to selling or renting certain diving products or services.

The largest international certification agencies that are currently recognized by most diving outlets for diver certification include:

See also

Reference list

Scuba diving, grouped
  1. ^ "Compact Oxford English Dictionary - scuba". Oxford University Press. http://www.askoxford.com/concise_oed/scuba?view=uk. 
  2. ^ a b c d e f g h i j US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. 2006. http://www.supsalv.org/00c3_publications.asp?destPage=00c3&pageID=3.9. Retrieved 2008-04-24. 
  3. ^ a b c d e f g h i j k Brubakk, Alf O; Neuman, Tom S (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 800. ISBN 0702025712. 
  4. ^ Vann RD (2004). "Lambertsen and O2: beginnings of operational physiology". Undersea Hyperb Med 31 (1): 21–31. PMID 15233157. http://archive.rubicon-foundation.org/3987. Retrieved 2008-04-25. 
  5. ^ Butler FK (2004). "Closed-circuit oxygen diving in the U.S. Navy". Undersea Hyperb Med 31 (1): 3–20. PMID 15233156. http://archive.rubicon-foundation.org/3986. Retrieved 2008-04-25. 
  6. ^ Hirschl, RB; et al (1995). "Liquid ventilatory in adults, children, and full-term neonates". Lancet 346: 1201–1202. doi:10.1016/S0140-6736(95)92903-7. 
  7. ^ Sekins, KM; et al (1999). "Recent innovation in total liquid ventilation system and component design". Biomedical instrumentation and technology 33: 277–284. PMID 10360218. 
  8. ^ a b Richardson, D; Menduno, M; Shreeves, K. (eds). (1996). "Proceedings of Rebreather Forum 2.0.". Diving Science and Technology Workshop.: 286. http://archive.rubicon-foundation.org/7555. Retrieved 2008-08-20. 
  9. ^ Hesser, CM; Fagraeus, L; Adolfson, J (1978). "Roles of nitrogen, oxygen, and carbon dioxide in compressed-air narcosis.". Undersea Biomed. Res. 5 (4): 391–400. ISSN 0093-5387. OCLC 2068005. PMID 734806. http://archive.rubicon-foundation.org/2810. Retrieved 2008-04-08. 
  10. ^ Brubakk, Alf O; Neuman, Tom S (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 304. ISBN 0702025712. 
  11. ^ Deaths During Skin and Scuba Diving in California in 1970
  12. ^ Is recreational diving safe?, por Ikeda, T y Ashida, H
  13. ^ Longphre, J. M.; P. J. DeNoble; R. E. Moon; R. D. Vann; J. J. Freiberger (2007). "First aid normobaric oxygen for the treatment of recreational diving injuries". Undersea Hyperb Med. 34 (1): 43–49. ISSN 1066-2936. OCLC 26915585. PMID 17393938. http://archive.rubicon-foundation.org/5514. Retrieved 2008-05-03. 
  14. ^ NOAA Diving Manual, 4th Edition, Best Publishing, 2001
  15. ^ "Thermal Conductivity", Georgia State University, accessed 15 February 2008
  16. ^ Weinberg, R. P.; E. D. Thalmann. (1990). "Effects of Hand and Foot Heating on Diver Thermal Balance". Naval Medical Research Institute Report 90-52. http://archive.rubicon-foundation.org/4247. Retrieved 2008-05-03. 
  17. ^ Nuckols ML, Giblo J, Wood-Putnam JL. (September 15–18, 2008). "Thermal Characteristics of Diving Garments When Using Argon as a Suit Inflation Gas.". Proceedings of the Oceans 08 MTS/IEEE Quebec, Canada Meeting (MTS/IEEE). http://archive.rubicon-foundation.org/7962. Retrieved 2009-04-17. 

Further reading

External links


Travel guide

Up to date as of January 14, 2010

From Wikitravel

Diving the wreck of the Zenobia, Larnaca, Cyprus
Diving the wreck of the Zenobia, Larnaca, Cyprus

This article is a travel topic.

Scuba diving is an activity in which you swim underwater for extended periods using Self-Contained Underwater Breathing Apparatus, hence the acronym SCUBA, or Scuba.

Scuba diving is an excellent way to see some very beautiful sites: Tropical coral diving sites with their colourful sea life are the most famous but other scuba diving attractions include tropical and temperate rocky reefs, shipwrecks, caverns and caves.

Scuba diving can also be a very relaxing sport and in many places it's very beginner friendly. Many dive sites are accessible (under the care of an instructor) after a short briefing and training dive. You can learn to dive far more quickly than you can learn snow sports, for example, and a high level of fitness and strength is not always necessary. It's also suitable for people with a number of physical disabilities. As long as you can use the breathing equipment and are able to successfully propel yourself underwater you may be able to dive (see also Stay healthy).

Related topics include Snorkeling, which generally refers to swimming on the surface while breathing through a snorkel, Free diving, which involves breath hold underwater swimming, and SNUBA, which provides a surface source of pressurised breathing air, supplied to the diver through a limited length of hose and a mouthpiece.

Destinations

Diving is a major travel activity: dedicated divers plan entire dive holidays, and others may want to include dive sites in their itineraries. Major dive destinations include:

Africa

Africa has a long coastline, and the coastal waters range from the warm tropical Red Sea, to the cool temperate west coast of southern Africa. The east coast of Africa is better known for diving destinations than the west coast or the Mediterranean coast, and there are good diving destinations scattered along the east coast from Egypt to South Africa, wherever accessibility and political stability allow.

The infrastructure varies enormously and is constantly changing. Availability of Nitrox, for example, is known from Egypt and South Africa. In some other places the availability of medical oxygen may be in question. Emergency medical facilities are also variable. Don't assume that anything is available at any specific destination. Ask and get written confirmation or book through certified operators and agents[1].

Djibouti

Djibouti has a unique ecosystem where the mix of the Red Sea and the Indian Ocean results in an abundance of marine life. Between the months of September and January Djibouti is home to resting migrating whale sharks. It is common to see many whale sharks, including juveniles, which tend to stay close to the coast during their visit.

Seven Brothers Islands is a major attraction to Djibouti waters. This breathtaking reef system is north of the Devils Cauldron, and comprises seven islands covering a vast area. Monumental drop-offs with stunning soft corals carpeting the walls, schooling fish and big pelagics can all be expected.

Egypt

The Egyptian coast along the Red Sea in both Africa and the Sinai peninsula is a favoured destination for Scuba diving and snorkeling. Various dive centers operate in each resort town or city to arrange both recreational and educational trips for all levels of experience and budgets.

Kenya

Madagascar

Malawi

Malawi is a landlocked country, but it has a long coastline on Lake Malawi, with good freshwater diving.

Mauritius

Mauritius is completely encircled by a coral barrier reef and is home to many sponges, sea anemones and a variety of multi-colored tropical reef fish such as the Damselfish, Trumpetfish, Boxfish, Clownfish and the Mauritian scorpionfish with its unique orange color.

Most of the Dive sites are located on the west coast around Flic-en-Flac, in the north, at Trou aux Biches or at the Northern Islands.

Besides the coral reefs, there are ship wrecks dating back to the 18th and 19th centuries, and ships sunk more recently which create beautiful artificial reefs.

The best time to go diving is from November to April when the visibility is very good.

The Mauritius Scuba Diving Association (MSDA)[2] can provide further information.

Some of the popular dive sites of Mauritius are:

  • Cathedral which is located off the Flic en Flac on the western coast of Mauritius.
  • Whale Rock
  • Roche Zozo, an underwater rock pinnacle.
  • Ile Ronde has a nearby submerged volcanic crater.

Mozambique

Mozambique is located on the southeast coast of Africa.

Mozambique has a tropical climate with two seasons, a wet season from October to March and a dry season from April to September. Rainfall is heavy along the coast and decreases in the north and south. Cyclones are common during the wet season.

Mozambique has nice coral, with colouful reef fish and invertebrates, but is known more for its abundance of manta rays, reef sharks, whale sharks and humpback whales.

Seychelles

South Africa

South Africa has sites spread along its coast that are well known for sharks and other large marine animals, but also have a large range of endemic smaller fish and invertebrates. The coastal sites range from tropical coral reefs in the north of KwaZulu-Natal, where the fish are typical Indo-Pacific tropical species, and very colourful, to cool temperate rocky reefs on the West Coast, where the fish life is relatively dull, and the largely endemic invertebrates provide the colour.

The annual sardine run up the east coast is justly famous, with huge baitballs and a large variety and number of predators, from Bryde's whales down through dolphins, sharks, gamefish and seabirds.

There are a large number of wrecks along the coast, some of which are regarded as good dive sites.

The inland sites are more usually used for training, technical and cave diving.

Major diving destinations include:

Tanzania

Includes the islands Zanzibar and Pemba.

Timor-Leste

Timor-Leste or East Timor is located in south-east Asia, just north-north-west of Darwin Australia.

The country has a tropical climate with two seasons, a wet season from October to March and a dry season from April to September. Diving is best between March and December.

With a 3000m deep Wetar Strait just off the north coast, a fantastic array of coral and sea life can be found, most of it straight off the shore. This is a world class dive spot that few know about. It is also a whale hot spot.

Asia

Spotted Moray Eel in Sabang, Philippines.
Spotted Moray Eel in Sabang, Philippines.

Scuba diving destinations in Asia are mostly concentrated in the Middle East and South East Asia, where the water is warm and visibility is usually good. These regions mostly have a tropical coral reef ecology, and there are a number of notable wreck diving sites.

Egypt

India

Andaman and Nicobar

The untapped potential here is huge, but for now diving is centered around Havelock Island, and while it's great you leave satisfied yet hungering for what you didn't see but know is out there. As tourism on the islands increase massive amounts of new dive sites should start to appear.

Lakshadweep Islands

Dive sites at Lakshadweep are centered around Agati, Kadmat and Bangaram islands.

Goa

Goa is India's top dive destination, but mostly just because it's the easiest to get to: visibility is usually only 5-6m. Diving season is mid-October to mid-May.

Indonesia

Bali

Menjangan Island in the north-west, and Tulamben (USS Liberty wreck) and Amed in the east, offer some of Asia's most pleasant and accessible shore diving through wrecks, walls and reefs. Divers visiting Bali often base themselves out of Lovina, Candidasa and Amed to access the sites.

The offshore island of Nusa Penida probably offers the most dramatic diving in Bali while the neighbouring island of Nusa Lembongan is well known as a teaching centre.

Gili Islands and Lombok
Flores and Komodo
Manado, Sulawesi

Intermediate to advanced diving, with occasionally strong currents. Wall diving at Bunaken.

Japan

Coral reefs on Ishigaki, Japan
Coral reefs on Ishigaki, Japan
Honshu

Izu Peninsula in Shizuoka prefecture is a popular destination for mainland Japan diving. The East Coast of Atami is most popular with dive operators for its accessibility and infrastructure, while the West Coast's sites are largely unspoiled, safeguarded from weekend crowds by its remoteness and lack of train stations.

Okinawa

The southern islands of Okinawa have great diving, but prices are steep: you can expect to pay upwards of $100 for two dives.

Miyako Islands
Yaeyama Islands

Manta rays, hammerheads and mysterious underwater ruins.

Jordan

  • Aqaba On the Gulf of Aqaba off the Red Sea

Malaysia

  • Perhentian Islands — home of sea turtles and many species of sharks on the east coast of Peninsular Malaysia. Great diving deals because of fierce competition.
  • Redang
  • Pulau Tioman — Splendid coral, fish, turtles and reef sharks off the Malaysian East Coast
  • Sipadan in Malaysian Borneo — Large biodiversity with 3000 species of fish and reef diving on a wall that descends 600m into the ocean
  • Mabul in Sabah, East Malaysia. Muck diving ecosystem.
  • Pulau Dayang For a less touristy but equally good dive spot, which can be reached by dive boat from Mersing

Maldives

Crystal clear water with over a thousand coral islets to explore.

Deep in the middle of the Indian Ocean, the entire country is built on coral reefs and has some of the best diving on the planet. Prices for accommodation and diving services are expensive, though, and currents can be strong on the outer reefs.

Oman

  • Muscat
  • Daymaniyat
  • Fahl Island
  • Salalah — has sea kelp and coral – an unusual combination of cold and warm sea organisms.

Papua

Philippines

  • Apo Island &mdash: Protected diving area for over 20 years. Healthy corals.
  • Boracay &mdash: The most popular place in the Philippines to become certified. Quality beginner diving as well as a few good intermediate dive sites.
  • Sabang %mdash: Also commonly refered to as Puerto Galera. Macro (i.e. small life photography) heaven. Approximately thirty dive sites that feature a dazzling variety of small sea life with the occasional shark, ray and/or turtle. Several sites are drift dives and often turn into (strong) current dives with the best diving (for coral and small life) being at 20m or 60 feet.
  • Panglao &mdash: Home of the Alona Beach - A mix of relaxation and diving. Dive the islands of Balicasag, Cabilao and Pamilacan from here.

Saudi Arabia

Notoriously difficult to visit, but hence very well-preserved, and now open to tourists who can book well in advance

  • Farasan Islands
  • Jeddah
  • Yanbu

Thailand

  • Ko Tao in south eastern Thailand: great for beginners and one of Asia's most popular places to get certified.
  • The Similan Islands in south western Thailand — Widely regarded as some of Thailand's best diving. 70 km due west of Phang Nga, best accessed via liveaboard or a lengthy boat ride from Khao Lak. The Krabi region (Ko Lanta, Ko Phi Phi, etc) nearby is similar and rather more accessible.

See One month of Southeast Asian diving and culture for a possible trip.

Europe

Diving destinations in Europe include the more popular international destinations in the Mediterranean and mostly domestic destinations in the rest of Europe. Exceptions include some famous wreck dives at Scapa Flow in the Orkney Islands and the fjords of Norway

Cyprus

The wreck of the Zenobia off Larnaca is among the best and most easily accessed in Europe.

Iceland

Diving in a crack between the continents in water as clear as it can get, being filtered by lava fields for decades.

Italy

  • Sardinia — Also known as Sardegna, has a cave system in Alghero, with crystal clear water and astonishing limestone cliffs, it is one of the more significant cave diving destinations in the Mediterranean Sea. Red coral, lobsters, groupers.
  • Sicily

Malta

Stunning limestone formations, steep dropoffs and good visibility make this one of the best diving destinations in the Mediterranean

North America

North America includes Central America, the Caribbean and Hawaii.

Aruba

Belize

Bonaire

Canada

Cayman Islands

Cuba

Maria la Gorda - popular scuba diving destination

Dominica

Located in the center of the Caribbean island archipelago, Dominica's dramatic landscape is as spectacular underwater as it is above. Dominica is one of the top dive destinations in the world, and has been rated in Scuba Diving Magazine #1 for Marine Life, #1 for Healthiest Marine Environment, #1 for Small Creatures, and #3 Dive Destination.[3]

Honduras

Martinique

  • Saint Pierre : Scuba dive at wrecks in the harbor. During the 1902 volcanic eruption, all but one of the ships in the harbor sank, leaving many wrecks as dive sites.

Mexico

  • Cabo San Lucas — on the southern tip of the Baja Peninsula is a meeting point of reef and blue water fish. While the number of dive sites are limited the variety of species makes up for it as do the viewing of the sand falls.
  • Cozumel — has excellent and very accessible diving making it one of the most popular diving destinations in the northern hemispheres. The area is well known for reef, wall and drift diving as well as for a lively top-side scene.
  • YucatanCancun and Playa del Carmen are well known for cave diving in addition to advanced diving in the labrynth of fresh water cenotes.

Saba

This small volcanic island is located south of Saint Martin and differs from other Caribbean islands as it features steep drop-offs and submerged pinnacles that are virtually untouched.

United States of America

  • Florida — Reef diving off the Florida Keys and Cave diving in the extensive limestone cave networks.
  • North Carolina — Wreck diving up to and beyond 130 feet deep. Sometimes referred to as the "Graveyard of the Atlantic" because of the numerous shipwrecks. Frequent opportunities to encounter Sand Tiger or Ragged Tooth sharks.
  • California: Monterey, Channel Islands, Farallon Islands.
  • Hawaii
  • Michigan: lake Michigan diving offers the most preserved shipwreck diving in the world.

Oceania

Diving a wreck off Wake Island
Diving a wreck off Wake Island

Australia

The coastline of Australia is very long and includes a considerable range of water temperatures and marine ecologies.

  • Great Barrier Reef -- large tropical reef system, most operators do sheltered easy diving. The reef is a few hours' boat ride from most of Far North Queensland. However the area has been over used and is in danger of being damaged beyond recovery.

Fiji

Micronesia

  • Palau
  • Saipan
  • Chuuk Lagoon -- wreck diving, including optional penetration, on a huge number of ship and aircraft wrecks from World War II's Operation Hailstorm.

New Zealand

Papua New Guinea

Madang — a town with fine scuba diving

Vanuatu

Intermediate level wreck diving, including penetration, on the President Coolidge, blue hole diving with excellent visibility.

South America

Brazil

Brazil offers many destinations for diving:

There are also liveaboards in the Northeastern region.

To dive in public parks (like Fernando de Noronha) one must be certified by one of the agencies recognized by IBAMA (Instituto Brasileiro de Administração do Meio Ambiente), a federal organ.

Colombia

Colombia has some of the cheapest diving in South America. A cheap place to learn is Taganga.

  • The islands of Isla Gorgona, San Andrés and Providencia have some really good diving.
  • A little known but excellent location for large pelagics (i.e hammerhead sharks, whale sharks etc.) is Malpelo Island. It is accessible by live aboard only.

Chile

Ecuador

  • Galapagos Islands - Darwin and Wolf Islands offer the opportunity to see schools of dozens of hammerhead sharks, while whale sharks and other large sea creatures are also frequently sighted.
A reef teeming with colorful life
A reef teeming with colorful life

It is best to learn diving from a competent instructor, as there are a number of skills important for your health and safety. It is an activity where there are a few things that must be done right or you may kill yourself. Experience and qualification of the instructor, while not a guarantee of competence, at least indicate that the instructor was trained and certified by an organisation which in some way strives for quality assurance, and allows some recourse if you are dissatisfied with the service. Aside from the complexities of assembling the equipment, diving has a number of risks that you need to understand, and safety procedures which you need to learn. There are also some basic skills that it is useful to practise under a teacher: the major one is controlling your buoyancy so that you aren't alternately sinking and floating but instead can swim along without yoyoing, and can ascend and surface at a controlled rate to avoid injury from rapid pressure changes.

Precisely because of these safety concerns, you will need to be trained and certified in order to be insured for medical treatment you need after a dive.

Beginner courses

As a first-time diver, you will learn to dive in open water with no decompression. The term "open water" refers to dive sites from which you can swim straight up to the surface (not caverns, for example). "No decompression" diving is diving timed so that you do not have to ascend in stages and wait long periods of time at various depths to expel excess gas from your system, meaning that in an emergency you can go slowly but directly to the surface without an undue risk of decompression sickness.

Open water certification

Open water certification courses are complete beginner level diving courses: they assume no experience, but after passing the course you will be certified as being able to dive in open water with a similarly qualified buddy diver but without an instructor's company, at least in cases where conditions are similar to those in your course.

Open water certification is close to mandatory: many insurance companies demand either that you dive with an instructor or that you dive with open water certification in order to insure you and many dive tours will require that you are certified to at least this level before they will take you diving.

Open water courses tend to take three or four days full-time although you can often arrange to do them part-time or in pieces over a period of time. The time is divided between: time in a classroom learning the theory of diving; time in a pool learning how to use the equipment and move around underwater; and several dives in open water under the care of your instructor. Some certification agencies now offer the classroom syllabus online, and you only need to do the pool and open water dives with an instructor. Certification tends to be progressive: you need to pass each module in order to proceed to the next. It's usually the case that you pay for the course, not the certification: paying the money does not guarantee that you will pass the course. That said, beginner courses are not very challenging and, barring medical or psychological issues, nearly all participants pass.

Some people recommend that you do the open water certification before a holiday rather than during it: you will need to be prepared to spend holiday time for time in a classroom otherwise, and the time on the course will seldom be spent at the most interesting dive sites. However, many travellers do do their open water certification on holiday, either because they didn't plan to start diving until they arrived, they don't live near dive sites, or they have a particular location in mind where they want to spend their first dives. It is also usually possible to do a open water referral where you do classroom and pool training with one instructor and then do the required open water dives and finish your certification with another. This can be used to do the preparatory work at home and the dives on your holiday. You may need to do both halves of the course under the same certification agency's syllabus: check if your preferred agency is in the Universal Referral Program [4].

Other beginner courses

If you only want to dive once or twice, or you want to try it before you commit to a full certification, there are often shorter courses (known as resort courses) available. They are 'taster' courses in which you receive basic training in the equipment and do an open water dive under the supervision of an instructor. They are not complete certifications and do not fully train you to plan your own dives with a buddy; you will need the close attention of an instructor at all times. If you intend to dive more than a few times in your life, a full open water certification is worth the cost.

These supervised dives and courses vary widely in quality and safety. You should check that you will be diving in a very small group (or ideally one-on-one with a certified instructor as your personal dive buddy); that you will be diving at a shallow depth (no more than 12 meters/40 feet); and that the conditions are as tranquil as the area permits: cold water and currents are more stressful to dive in than still warm water.

Some certification agencies provide a syllabus for a resort-style course that will allow you to try an open water dive with a small amount of training and an instructor close by; for example PADI's "Discover Scuba" and "Scuba Diver" courses or SSI's "Try Scuba" and "Passport Diver" courses. These courses usually include part of the material for an open water certification, so that when you complete the short course you can go on to finish the open water course without needing to do the full course from the beginning.

Some dive resorts offer their own supervised diving or resort courses. If your resort certification is only awarded by that resort and not by one of the certification agencies then you will not be able to use it at most other resorts and it is unlikely to count towards a full certification.

Certification agencies

There are a number of agencies which certify divers. They work by training and certifying instructors in their syllabus and teaching methods, and then allowing those instructors to certify individual divers. This section lists some of the certification agencies and their recreational (rather than professional or teaching) certifications. Your choice of certification will depend on a number of factors, primarily which certification agencies have a presence in the area you learn in, and in the areas you wish to dive in.

All reputable dive operators will require certification of your skills in the form of a certification card (C-card) from a recognized agency. This does not need to be the same agency that their own instructors work with: for example, a CMAS or SSI certified diver can dive with a shop that certifies under PADI. The requirement for certification is often also enforced where the customer wishes to buy Scuba equipment or have cylinders filled, but this is not universal, as in some countries there is no legal obligation for a recreational diver to be certified.

Recognised recreational certification agencies include:

  • ACUC: The American Canadian Underwater Certifications [5]
  • ANDI: American Nitrox Divers International,
  • BSAC: The British Sub Aqua Club [6], bases its training on a network of affiliated clubs.
  • CMAS: The French-based Confédération Mondiale des Activités Subaquatiques [7] , a volunteer-run amateur organization that takes a more comprehensive approach than many of the commercial agencies. There are national certification agencies affiliated to CMAS for most countries where training is done under their standards. Certification by all CMAS agencies is considered to be equivalent, but national agencies do not all necessarily provide the same range of certification.
  • GUE: Global Underwater Explorers [8], concentrates on technical and cave diving specialities.
  • IANTD: International Association of Nitrox Technical Divers.
  • IDEA: The International Diving Educators Association [9]
  • ISI: The Independent Scuba Instructors[10]
  • NAPI: The National Association of Professional Instructors, does not train directly, but issues certification based on recognition of prior learning and experience.
  • NAUI: The National Association of Underwater Instructors [11], US-based, is the oldest recreational scuba certification agency.
  • PADI: The Professional Association of Diving Instructors [12], the largest scuba certification agency, a commercial agency targeted towards recreational divers who want to learn quickly.
  • PDIC: The Professional Diving Instructors Corporation [13]
  • SDI/TDI: The Scuba Divers International/Technical Divers International [14] , a certification agency designed to train with an emphasis on practical diving skills. SDI focuses on the recreational side of scuba diving and TDI is the mother branch that specializes in Technical Diving.
  • SSI: Scuba Schools International [15], another large commercial agency.

Advanced training

After completing a beginner level dive course, you can do additional courses to increase your skills or to pursue particular interests.

Post-beginner skills involve learning to dive in new or more difficult conditions or learning to dive using different equipment. There are several reasons you might pursue more skills in addition to the simple challenge: increased safety knowledge or a desire to dive at particular sites that need those skills are among them. Often you will need to do a formal course in new dive skills because centers running dives using those skills will require evidence that you are properly trained. Post-beginner skills that usually require training include: diving using oxygen enriched air ("nitrox"), deeper diving (optionally including decompression), wreck diving and cave diving. A diving rescue course is worthwhile if you dive regularly, whether or not you continue as a no-compression open water diver. Most certification agencies have courses in these skills and some wrap a number of them up into various 'Advanced' certifications. Many divers proceed to more difficult conditions (cool water, diving at night) without formal courses, but they are available if you want them.

Interests are particular reasons why you dive and include: underwater photography and videography; marine life identification; and marine life conservation. Many of the dive certification agencies have guided dives or courses in these fields but you may also be able to learn them informally from self-study, practise and fellow divers.

Get in

There are three major types of travelling to your dive site: liveaboards where you stay on the boat, day trips where you take a boat trip out to your dive site and back in the same day, and shore diving where you get in from the land.

Liveaboard traffic in the Similan Islands
Liveaboard traffic in the Similan Islands
Liveaboard in the Philippines
Liveaboard in the Philippines

Many divers prefer liveaboards, where they sleep on the dive boat. This can save on accommodation costs, allow for more diving, and make it easy to get to know your fellow divers. Liveaboards range from 1 night in length to a fortnight or more. Liveaboards typically allow between 3 and 5 dives per day (depending on time and dive tables). The accommodation quality ranges from backpacker-esque, with 4-share cabins and showers shared between multiple cabins, to luxury cruise style accommodations. If you haven't opted for a luxury liveaboard, you will get your dives for about two thirds the cost of a day trip on a boat, even leaving aside any savings on accommodation.

When travelling on a liveaboard:

  • pack as little as possible: a few changes of weather appropriate clothes, sleep gear, toiletries, light-weight entertainment (non-electronic is best) and your dive gear if you aren't renting
  • space is always at a premium, and it's easy to get things mixed up and annoy fellow divers, keep your dive gear together in a tub or bag on the deck
  • label your possessions with your name; they will be mixed up with a lot of similar looking equipment
  • dry off before heading into the interior of the boat so that the floors aren't constantly wet
  • most boats have a limited supply of fresh water for drinking and washing: have short showers

If you haven't spent much time on boats, you may not be aware of whether or not you get sea-sick. Some divers have an unhappy first dive trip on boats because they weren't aware that they suffer from sea-sickness. If you haven't been on a boat in open before, especially if you suffer from other kinds of motion sickness, you might be best off doing a few day trips on dive boats and experimenting with sea-sickness medication before committing to a liveaboard. That said, liveaboard trips for your first dives can be an excellent introduction, because you will usually do more than the bare minimum dives required for certification. Instead, you will get a lot of additional dive experience.

The main activity on a liveaboard is the diving: you will wake early for your first briefing and only complete the last dive at or after sunset, day after day. During the surface time you need to let nitrogen out of your body you will usually be eating or sleeping. Liveaboard trips are excellent for dedicated divers, but may not suit divers who don't want to spend their entire holiday gearing up, diving, getting their gear off, eating and sleeping.

On a day trip

Many dive sites are accessible by a boat ride of a few minutes to a few hours from shore, so you can go out to the site on a boat, dive and return to your land-based accommodation at night. Boats which conduct day trips range from rubber dinghies equipped with an outboard motor to larger boats with indoor areas and hot showers. Longer day trips tend to entail nicer boats. Dive trips that take much of a day will usually include a catered lunch and perhaps some smaller snacks in the price. On a per-dive basis day trips are usually more expensive than liveaboards, so divers choose to day-trip when they want to only have a few dives at a particular set of sites, or when they want to alternate diving with other activities.

As with liveaboards, some people take their first boat trip unaware of the possibility of sea-sickness. If you think you're at all likely to suffer (ie if you get sick in cars or other vehicles), you should take some preventative measures an hour before leaving on the boat.

Be aware that not all day trip boats will have toilet facilities. Since it's not a good idea to dehydrate yourself before diving you may have to accept that you will have to urinate either over the side of the boat or into a bucket which you'll tip over the side and rinse. This can be a little more difficult for women to do quickly and safely. If this is unacceptable to you be sure to check on the boat's facilities in advance.

Some day trips are organised by dedicated dive resorts, which bundle day trips and land based accommodations into one price. You usually won't be compelled to stay with them in order to do their trips, but it may be cheaper. During peak times you may need to dive on most days of your stay to take advantage of the deal.

From shore

Shore-based dives are dives where the site is close enough to the water's edge that a diver can swim out into the water and descend to the dive site. Shore diving is cheaper than boat diving: unless you're paying an instructor or guide you only need to pay for any equipment you want to hire. You will often find a dive shop or dive resort conveniently located near a good shore dive site.

Shore diving can be tiring if the site is not extremely close to the shore. Rescues may not be as fast as from a boat which will have spotters looking out for divers in distress. Be sure to check the length of the swim to your chosen site and its difficulty: shore dives are not necessarily easier than boat dives.

Some shore dive sites are either only accessible, or are much safer and easier dives, at a certain tide height. Unlike on a boat dive, where the boat operator can time the visit to correspond to the right tide if need be, shore divers need to find out about tidal sites and tide times themselves. It's also not impossible to get sea-sick on a shore dive, particularly if swimming or resting on a choppy surface. It's easier to avoid though as most people find that dropping below the surface where there is less motion helps or removes the nausea.

Hawksbill Turtle in Sabang (Philippines)
Hawksbill Turtle in Sabang (Philippines)
Bull Shark in Palau
Bull Shark in Palau

Different dive sites have different things to offer:

  • Many divers dive in order to see marine life. Particular favourites include turtles, mantas and especially sharks. The fascination with sharks can sometimes escape non-diving friends but most species of shark don't pose a threat to divers and they are beautiful to watch. Diving with a whale shark is one of the most highly prized diving experiences. Others develop an interest in reef life, including the enormous range of invertebrates that live on the bottom, and the often colourful fish that live around them.
  • Divers interested in marine life or just in new experiences like to dive at night. Nocturnal marine life is different, and sometimes more active, than daytime marine life. Night diving does not require added equipment above daytime diving other than a powerful torch, and is often one of the first new experiences available to newly certified divers. Often the use of artificial light will bring out an intensity of colour that goes unnoticed during the day, when the water absorbs much of the colour at depth.
  • Tropical coral reef diving surrounds you with a sometimes unbelievable amount of colour and activity. Diving in tropical water is also comfortable and often low stress because the water is very clear. You are vulnerable to stings and to nasty coral scratches which are easily infected though: many divers choose to wear a full length thin wetsuit even if the water is warm enough to dive naked!
  • Rocky reefs occur in tropical, temperate and polar waters, and support ecosystems which may range from quite similar to coral reefs, to considerably different. In many regions on rocky reefs, instead of colourful fish, the rocks are encrusted with sponges, soft corals, colonial ascidians, bryozoans and a wide range of mobile invertebrates, which together contribute to an overall effect as colourful as a tropical reef.
  • Wrecks have three appeals: fish life, historical interest and technical difficulty. Wrecks that have been sunk for some time become artificial reefs, attracting fish life and coral. The trade-off is that this tends to happen in warmer water, which will also cause the wreck to disintegrate more rapidly. Wrecks in colder water will attract less marine life but retain historical interest, particularly those of ships that were lost at sea rather than stripped of artefacts and scuttled. Wrecks of planes, particularly those shot down in wartime, are also popular. Divers can actually enter some wrecks: however this is relatively hazardous and requires training and experience well beyond introductory open water training.
  • Caves have an appeal to some divers, who enjoy the feeling of going where few people have ventured, and some caves provide spectacular surroundings. This environment is inherently hazardous and requires training and experience far beyond introductory open water certification.
  • Many divers enjoy underwater photography or underwater videography. To take pictures or video while diving, you will need a waterproof housing for your camera or video recorder. Many dive shops also have rentable cameras.

Buy

Scuba diving equipment has standardised into a number of basic pieces, together with some optional pieces for certain conditions. Most dive centers will have all the standard equipment for rental, and as with many equipment-heavy sports it can be worthwhile to use rental equipment for a while before you decide to purchase your own.

Standard equipment is:

  • A mask which provides an air space over the eyes and nose with transparent viewport which may include corrective lenses. This allows you to focus and see clearly under water.
  • A snorkel (a short curved tube with a mouth grip allowing you to breathe at the surface with your face underwater)
  • Fins for propelling yourself underwater
  • An exposure suit: a wetsuit for warm water or a dry suit for colder water, perhaps with boots, gloves and hood. A skin suit is a very thin wet suit which is mainly intended as protection from stings, scratches, chafe and sunburn in tropical water.
  • A Buoyancy Control Device (BCD): an inflatable jacket allowing you to sink or float by deflating and inflating it, and to neutralise buoyancy at any depth so that you can stay there without effort.
  • A compressed air tank to supply breating air during the dive.
  • A regulator: apparatus for delivering air from the tank to your mouth on demand at ambient pressure.
  • A weight belt, weight harness or weight pouches integrated with the BCD, to compensate for the buoyancy of the exposure suit.
  • A depth gauge
  • A Submersible Pressure Gauge (SPG), which shows the pressure of air remaining in the tank.
  • A timing device

Optional equipment includes:

  • A dive computer to record depth and times and to indicate decompression requirements. It is usually used to avoid the requirement for decompression stops.
  • Enriched air (extra oxygen) tanks
  • Underwater photography or videography equipment. Disposable 'waterproof' cameras and cheaper underwater housings are generally only guaranteed to be leak free to about 3 meters/9 feet in depth, you will want one waterproof to at least 30 meters/100 feet. Properly rated housings are manufactured by many major camera manufacturers, and for more expensive cameras and video cameras housings are made by third parties.

Check the warranty conditions carefully, especially on expensive electronic equipment: water damage is usually not covered even on the housing warranties. Specialist dive insurance may provide insurance against loss of or damage to your equipment while diving, general travel insurance usually will not, even if it covers the medical aspects of diving.

Rent or buy?

The three pieces of equipment every diver should buy for themselves and bring along are fins, snorkel and mask: these need to fit to your body closely to be safe and comfortable, they're fairly cheap, and they don't need that much space. Up next is an exposure suit (wetsuit or drysuit), which is also better fitted than off the shelf, but is bulkier to carry along.

But the bigger question for most divers is whether they should also make an investment in a full set of scuba gear, namely regulators, gauges and BCD. In purely financial terms, you have to dive quite a bit to save money this way, especially when you factor in yearly servicing fees. However, perhaps a bigger factor is safety: not only can you ensure that your own gear is kept properly serviced, but you will already be familiar with the controls and performance of your own gear, which makes diving easier and increases the chances of you acting correctly in an emergency.

The two items almost nobody brings along are tanks and weights, as these are extremely heavy and bulky, and practically always included in the dive price. For some destinations well and truly off the beaten track though (say, the Red Sea coast of Sudan) you may have to take along not just these, but the compressor too!

Work

The recreational scuba diving industry in popular diving areas is usually partly staffed by travellers, mostly divers themselves funding their diving.

In order to actually be paid to dive in the recreational scuba industry, you will need to either be a certified divemaster or an instructor. Divemasters look after paying divers on the boat, handle any problems they have and tell them about the dive sites. They might also lead underwater guided tours of dive sites and assist in diving classes. Instructors run the diving classes themselves. You train as a divemaster first and then qualify for instructor training.

Divemaster and instructor certifications are awarded by the same agencies that award the other recreational diving certification. To enter the instrictor training programmes you will generally need to be a skilled diver and have at the barest minimum somewhere in the order of 100 dives experience. Many instructors trainers recommend a great deal more experience before starting. Divemaster and instructor certifications are expensive to gain and expensive to keep, as you will need to renew them and also may have to pay an insurance premium.

Other work available to travellers in the diving industry includes retail, boat operating and repairing, dive equipment maintenence and cooking. If you're travelling out on dive boats you will often be expected to be able to dive, and possibly to hold diver rescue and first aid certifications, even if you're notionally the cook. For both diving and boat work, some experience in hospitality is valuable, although not always necessary.

Almost all diving work, especially in extremely popular tropical diving locations, is badly paid. In some countries, divemasters are expected to work for tips alone. You will generally make enough to cover the basic expenses of a backpacker lifestyle and will usually get some free diving (although not as much as you expect).

In some countries any commercial (paid) underwater work other than that directly connected to recreational diving is regulated by legislation. In many cases this will require the working diver to be registered as a commercial diver and to comply with health and safety regulations. Check the local situation before taking on any such work, as although it will often get by under the radar, it may be technically illegal and if anything goes wrong the foreigner is usually the scapegoat. In other countries there may be no laws at all controlling underwater work, however these are usually also the countries where standards of safety and protection of the worker are likely to be lowest.

Stay safe

The obvious safety concern with diving is that you must rely on your equipment to deliver you air. For this reason, scuba equipment is subject to rigorous testing according to various standards at the design and production stages. Your part of ensuring your own safety is making sure that you are adequately trained and prepared for any dive you do, and that your equipment is suitable for the dive and functioning correctly. Do not assume that rental equipment is in good order: test it yourself.

The other side of this is to ensure that the air you breathe is safe. Most popular diving destinations will provide air fills from a suitable compressor in good condition and adequately filtered. Other places may be more haphazard and compressors that are in bad condition, dirty filters, poor installations, external sources of contamination and careless or unscrupulous operators may provide you with contaminated air. Contamination at levels which may be imperceptible or merely give you a headache or mild nausea on the surface can cause loss of conciousness underwater, often leading to drowning.

Being familiar with symptoms of equipment failure and recovery techniques obviously improves your safety. Your training will include information about performing basic safety checks on your equipment and about other guidelines. Further training is available in specialty courses.

If you're diving regularly you will probably want to take courses in emergency diving procedures and in first aid including CPR.

Basic safety precautions

The basic precautions you should take for safe diving are:

  • Have an agreed plan for every dive, including where you expect to go, how you will manage your air supply and what you and others will do if something unexpected happens (common problems are getting low on air, getting lost or losing your buddy)
  • Do not dive alone, always dive with a partner (a "buddy") who will stay close to you. Typically regulators have a second mouthpiece you can lend a buddy if they are out of air. Remember that a buddy who is not in reach in an emergency or who is not competent or willing to assist is no buddy at all, and that a buddy has no legal obligation to assist if it may endanger him or herself to do so. Do not allow the dive operator to pair you with someone whom you could not assist or who would not be able to assist you.
  • Do not dive in unfamiliar conditions without an orientation from a suitably competent person, or you may find your skills are not adequate to the task. This is a common problem for divers who are accustomed to warm, calm water and find themselves under stess the first time they dive in cold rough water, or in a current.
  • Do not dive in unfamiliar areas without a guide or appropriate orientation. Do some introductory dives or a dive orientation with a divemaster or diver with local experience.
  • Do not dive outside your training and experience, for example, diving deeper than you trained for, or diving in confined spaces when you're only certified for open water.
  • Do not dive with unfamiliar equipment except in very easy conditions, where any problems can be sorted out without major inconvenience or risk. Get your weights sorted out in shallow water, make sure the regulator has no leaks, and that the harness fits properly before going on a deep dive. Many divers have no idea of how much weight they will need with an unfamiliar exposure suit, and almost none will get it right first time.
  • Do not dive when impaired, e.g. by fatigue or alcohol.
  • If diving in a group led by a guide, do not neglect your own planning and air management and if necessary plan to ascend early without the guide. Divemasters vary in skill, but even the best will not substitute for taking responsibility for yourself.
  • If you feel overly anxious about the dive, or feel you may not be fully qualified for the conditions, you have the absolute, unconditional right to end the dive without having to justify your decision. Ultimately, you are responsible for deciding if any particular dive is right for you.
  • Check the air you will be breathing. It should have no smell or taste and should leave no mark when passed through a white cloth. These tests, if passed, do not guarantee that there are no contaminants, but if failed, dont breathe it. If you have any doubt, ask the shop to show you the latest air quality test results. Some places may not require this to be available, in which case a look at the compressor installation can tell you a lot. If the operator refuses to give this information, decide for yourself whether it is a good idea to stake your life on their product.
  • Dive with reputable and competent operators. Find out beforehand what the qualifications are of their skippers and divemasters, and what emergency facilities are available. You can still choose to dive with a less than ideal operation, but it is then an informed choice. Litigation after the accident is a waste of time and money in some parts of the world.

Checklist on potential dive operators

A few questions you could ask the dive operator before booking when planning a dive vacation to an unfamiliar region.

  • What are the qualifications of the skipper and divemaster?
    • Is a member of the crew qualified in basic first aid and oxygen administration.
    • Do they have emergency oxygen administration equipment on site and on the boat?
  • What is the local air quality standard, and how is it enforced?
  • How are seaworthiness of the dive boat and competence of the crew enforced?
  • What emergency facilities are available in case of an accident?
    • Search and recovery.
    • Medical evacuation.
    • Recompression.
    • First aid.
    • Medical treatment facilities.
  • How do they monitor the time that a diver has been off the boat and whether all the correct divers are back on board before leaving the site?

Standards for these items vary enormously. Do not assume that they will be much the same as at home. Oxygen is unavailable some places, and there are countries that do not have any recompression facilities at all. The last item may look a little trivial, but even in countries where safety standards are taken seriously, divers are occasionally left behind by accident, and it has happened that the right number of divers were on the boat, but some of them had dived from another boat, so a simple head count is not always sufficient.

Respect

Many dive sites are ecologically or historically sensitive areas. Dive tourism has the advantage of providing a reason to preserve many sensitive sites in order to keep the divers coming: for example, dive tourism may provide an incentive to control overfishing on divable reefs. However divers do themselves present a threat to many sites, having the potential to either directly damage them or subtly influence their characteristics. In order to help preserve dive sites:

  • Look but don't touch, be it the bottom, coral, marine life or wrecks.
  • Don't take souvenirs as everything you take is one less thing for future divers to look at, and often one less home for sea creatures. This is also illegal in some areas in the case of both protected marine sanctuaries and wrecks.
  • Learn good buoyancy control, so that you can avoid accidental damage to the site from crashing into things
  • Don't feed the fish, as it alters their natural feeding patterns

Some dive organizations promote a diving variant of the leave no trace motto: "take nothing but photographs, leave nothing but bubbles."

Stay healthy

Health conditions which prevent diving

Any medical condition which affects your respiratory or cardiovascular systems, or which may render you suddenly and unexpectedly unable to respond quickly or at all, might mean you cannot dive. Common contraindications are asthma, epilepsy, diabetes and heart disease. If you have any of these, or other illnesses which might cause similar problems, consult a doctor before diving. A physician with a knowledge of dive medicine and diver needs is best, particularly if you have a condition like asthma and want an informed opinion about whether your particular case means you can't dive.

Most dive courses will require a detailed medical history from you or a doctor before you begin diving.

Other health conditions which may temporarily prevent you from diving safely include:

  • Seasickness
  • Drugs and medications (consult a diving medical specialist if in doubt)
  • Alcohol and recreational drugs
  • Pregnancy
  • Nervous system disorders
  • Some cancers
  • Hepatitis, Malaria, and any illness causing fever or significantly impaired strength, judgement or cardivascular condition.

With some, it is the condition itself, and others, it is the drugs that are given for the condition that exclude one from diving. Unfortunately, the medical profession doesn't give black and white answers and some of the conditions require the diver to accept the risk and responsibility for the decision. Research is being conducted by various agencies around the world all the time and official medical opinion and policies do change from time to time.

Pressure related illnesses

In scuba diving, air is delivered to your lungs at the surrounding water pressure. Breathing air at high pressure can contibute towards a number of illnesses:

  • lung overexpansion in which high pressure air trapped in your lungs expands as you ascend, damaging your lungs and possibly forcing air into your bloodstream (an arterial gas embolism)
  • decompression sickness ("the bends") in which dissolved nitrogen in your body forms gas bubbles as you ascend, blocking blood supply to limbs or organs
  • nitrogen narcosis in which nitrogen causes impairment similar to drunkenness
  • oxygen toxicity in which oxygen poisons your nervous system or lungs

All of these illnesses and their prevention will be discussed during diver training. Not all of them are fully preventable, hence you must be alert to the risk and know how to seek appropriate treatment. Always know how to contact the local emergency services and the diver emergency services (if they exist) before a dive.

Preventing dive-related illness

In addition to observing the time, depth and ascent rate limits you will be taught in training, there are some other things you can do to lower the chances of a pressure related illness. Before a dive trip and when diving , it is wise to:

  • Be well hydrated. Dehydration is not only a health concern in and of itself, but is also a contributing factor to many cases of decompression sickness.
  • Limit your alcohol intake, partly because of its intoxicating effects and partly because it dehydrates you.
  • Avoid diving with blocked sinuses as high pressure air that enters them during the dive may not be able to exit, causing a painful "reverse block" that may take days to clear.
  • Avoid ascending to a higher altitude soon after diving; in particular, do not fly in most aircraft (commercial aircraft included) as they are rarely pressurised to sea level. Divers Alert Network (DAN) [16] recommends [17] waiting at least 12 hours after a single dive with no decompression stop before ascending, 18 hours after multiple dives without decompression stops, and more time again if there were decompression stops. Ascending sooner puts you at risk of decompression sickness.

There are several scuba emergency telephone hotlines set up in different areas of the world, many of which are provided by DAN [18] , which can advise on your symptoms and sometimes organise rescues and treatment (however, you will still have to pay for both, unless covered by insurance). Keep a note of your local hotline among your dive gear.

Diving in high altitude lakes

While diving at high altitude lakes, the risk for decompression sickness increases. Due to a lower atmospheric pressure in the environment, special dive tables should be used. These allow for the pressure difference correction factors to avoid decompression sickness.

Preventing sea sickness

A substantial number of boat divers will experience some sea sickness. You are probably more vulnerable if you experience other forms of motion sickness, eg getting sick in cars. Sea sickness, because of the many ways in which the boat can move, is usually more severe than car sickness. The upside, such as it is, is that as under the water is much calmer than the surface almost all sufferers find that their nausea vanishes within a few minutes of beginning to dive. If you are feeling ill but able to get your gear together, you should still be able to have a good dive.

Sea sickness can be prevented for many people with the use of travel sickness prevention medication from pharmacists. Meclizine and dimenhydrinate (US brand name Dramamine) are commonly used for prevention of seasickness, but both have the dangerous side effect of making you drowsy, and the effect seems to be amplified underwater. Try them out before you dive, so you can judge your own reaction, and consider taking only half a dose. Alternatives include scopolamine patches (also known as hyoscine or "transderm scop"), which are very effective but often require a prescription; cinnarizine (Sturgeron), which is popular in Europe but poorly available elsewhere.

If your sea sickness is mild, you may be better off using natural remedies like ginger or simply staying near the centre of the boat, avoiding unnecessary motion, and looking at the horizon. However, severe nausea is extremely uncomfortable and vomiting will dehydrate you: if you suffer sea sickness this badly, or think you are likely to, you might find that the side effects are much easier to deal with than the nausea. On the other hand, most divers find that sea sickness is quickly relieved once the dive has started and you've escaped the choppy surface, and even if worst comes to worst, it's entirely possible to vomit through your regulator.(Do remember to purge well before taking your next breath).

If you are taking medication to prevent sea sickness, you should begin taking it well before you get on the boat so that it can be absorbed by the time the motion begins. Taking it an hour before boarding is effective; this will also give you some time to adjust to any drowsiness. Divers taking overnight trips sometimes begin taking medication the night before departure.

A boat briefing will often include instructions on what to do if you think you're likely to vomit. If these aren't given and you forget to ask, the general etiquette is to go downwind (usually the rear of the boat) so that it doesn't blow into anyone's face, and to the opposite side to the ladder, and vomit overboard. Ask someone to accompany you so that they can make sure you're safe and won't fall overboard.

Preventing injuries

There are some injury risks that diving exposes you to. This is dependent on the site. For example, coral reef dives carry the risk of coral cuts, which can take months to heal well, and of stings and bites from venomous marine life. Educate yourself about risks in particular environments and particular sites and pay attention to dive briefings.

You can dramatically reduce the risk of injury by exercising caution and not interfering with the state of the dive site (e.g. by provoking the marine life or disturbing the bottom). Assume that everything is dangerous (poisonous, sharp, aggressive, etc.) and you'll keep yourself out of harm's way by not being tempted to touch anything.

One of the functions of the exposure suit is protection from external injury. Thick and strong suits will protect against cuts from coral, barnacles, or sharp edges of wrecks, thinner suits will protect against jellyfish, fire coral and similar organisms.

Insurance

It is very important to be insured for both general medical treatment needed for dive related illnesses and injuries, and in particular for decompression sickness treatment, which involves some hours in a recompression chamber. Recompression can be extremely expensive, around US$6000 an hour, and is specifically excluded by some insurance policies. In addition you should be insured for evacuation, as evacuation from boats by the emergency services is typically conducted from the air and is also very expensive.

There are many dive insurance policies which cover medical treatment needed after diving, including recompression. Some are associated with the certification agencies or with dive resort organisations. Typical prices are about US$500 per year for insurance for dives to less than 4 meters and US$1200 per year for coverage to any depth you have trained for. Less expensive group policies are also available from DAN [19]. In addition dive resorts and dive tour operators will often have insurance for divers who are injured or become ill on dives they conduct.

Many general travel insurance policies cover diving if you are certified or with an instructor, but check the terms first: some also exclude scuba diving.

This is a guide article. It has good, detailed information covering the entire topic. Plunge forward and help us make it a star!

Simple English

and coral]]Scuba Diving is a recreational activity, where people (called "scuba divers", or simply "divers") can swim underwater for a long time, using a tank filled with compressed air. The tank is a large metal cylinder made of steel or aluminum.   The divers have special equipment called BCD's (buoyancy control device) to control whether they float or sink they can add air or remove air by using dump valves or an inflator on their secondary regulator. They also use a Regulator.  A regulator is a piece of equipment which connects to the tank, and controls how much air is sent from the tank to the diver it helps adjust the air to the pressure that the diver is at so they can breathe properly at any depth. It helps the diver to breathe in from the tank, and out to the water.

Divers also use other equipment. They wear a mask to see through, fins on their feet to swim better, and a wetsuit to keep them warm under water because water makes you cold four times as fast as air.

The word Scuba is an acronym from Self-Contained Underwater Breathing Apparatus.


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