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Scuba diving is swimming underwater, or taking part in another activity, while using a scuba set. This article refers to underwater diving by humans For other uses of the term diving see Dive and Diving Underwater diving is A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. [1] By carrying a source of breathing gas (usually compressed air)[2], the scuba diver is able to stay underwater longer than with the simple breath-holding techniques used in snorkeling and free-diving, and is not hindered by air lines to a remote air source. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such Compressed air Underwater is a term describing the realm below the surface of Water where the water exists in a natural feature (called a body of water) such as an Ocean Snorkeling ( British spelling: snorkelling) is the practice of Swimming at the surface of a body of water while equipped with a Diving mask, a Free diving is any of various aquatic activities that share the practice of breath-holding Underwater diving. See also Airline (disambiguation For the Air Line Rail trail in central Connecticut see Airline State Park. The scuba diver typically swims underwater by using fins attached to the feet. However, some divers also move around with the assistance of a DPV (diver propulsion vehicle), commonly called a "scooter", or by using surface-tethered devices called sleds pulled by a boat. A Diver Propulsion Vehicle or a DPV is an item of Diving equipment used by scuba divers to increase their range while underwater where their endurance is

For the history of diving, see Timeline of underwater technology. This is a Timeline of Underwater Technology. The entries marked ## are about Decompression tables Pre-industrial

Scuba divers observing fish and coral
Scuba divers observing fish and coral

Contents

Etymology

The term SCUBA arose during World War II and originally referred to United States combat frogmen's oxygen rebreathers, developed by Dr. Christian Lambertsen for underwater warfare. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including A frogman is someone who is trained to dive or swim in a military capacity often in combat A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas Christian James Lambertsen, MD, DSc (Hon (b 15 May, 1917) is an American environmental and Diving medicine [2][3][4] Today, scuba typically refers to the in-line open-circuit equipment, 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. Émile Gagnan (November 1900 – 1979 was a French Engineer and co-inventor (together with Jacques-Yves Cousteau) of the demand-valve used for the first Jacques-Yves Cousteau ( 11 June 1910 – 25 June 1997) was a French naval officer explorer, Ecologist, However, rebreathers (both semi-closed circuit and closed circuit) are also self-contained systems (as opposed to surface-supplied systems) and are therefore classified as scuba. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas

Although the SCUBA is an acronym for "self-contained underwater breathing apparatus", usage is mainly as a normal word "scuba", it has become acceptable to refer to scuba as "scuba equipment" or "scuba apparatus" — an example of the linguistic RAS syndrome. A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. Acronyms, initialisms, and alphabetisms are Abbreviations that are formed using the initial components in a phrase or name A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. RAS syndrome stands for "Redundant Acronym Syndrome syndrome" and refers to the use of one of the words that make up an Initialism or Acronym as well as

Types of diving

Divemaster ready to dive Shark and Yolanda reef at Rās Muhammad, Sharm el-Sheikh.
Divemaster ready to dive Shark and Yolanda reef at Rās Muhammad, Sharm el-Sheikh. Sharm el Sheikh (شرم الشيخ Sharm al-Shaykh) often known simply as "Sharm" is a city situated on the southern tip of the Sinai Peninsula, in

Scuba diving is still evolving, but general classifications have grown to describe various diving activities. These classifications include:

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. Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. A frogman is someone who is trained to dive or swim in a military capacity often in combat Naval diving is a branch of Professional diving carried out by world navies. Police diving is a branch of Professional diving carried out by Police services Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. Recreational diving or sport diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment Diver rescue, following an accident is the process of avoiding or limiting further exposure to diving hazards and bringing a SCUBA diver to safety Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority Cave diving is a type of Technical diving in which specialized SCUBA equipment is used to enable the exploration of natural or artificial Caves which are Cave diving is a type of Technical diving in which specialized SCUBA equipment is used to enable the exploration of natural or artificial Caves which are The meaning of the term deep diving is a form of Technical diving. Ice diving is a type of Penetration diving where the dive takes place under Ice. Wreck diving is a type of Recreational diving where Shipwrecks are explored An aquarium (plural aquariums or aquaria) is a Vivarium consisting of at least one transparent side in which Water -dwelling Plants A public aquarium (plural public aquaria or public aquariums) is the aquatic counterpart of a Zoo, housing living aquatic species for viewing Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. A boat is a Watercraft of modest size designed to float or plane on water and provide transport over it A ship /ʃɪp/ is a large vessel that floats on water Ships are generally distinguished from Boats based on size Naval diving is a branch of Professional diving carried out by world navies. Cave diving is a type of Technical diving in which specialized SCUBA equipment is used to enable the exploration of natural or artificial Caves which are Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority Recreational diving or sport diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment A harbor or harbour (see spelling differences) or haven, is a place where ships may shelter from the Weather or are stored Water is a common Chemical substance that is essential for the survival of all known forms of Life. Drainage is the natural or artificial removal of surface and sub-surface water from a given area Petroleum ( L petroleum, from Greek πετρέλαιον, lit Offshore construction is the installation of structures and pipelines in a marine environment for the production and transmission of oil and Gas. Demolition is the opposite of Construction: the tearing-down of Buildings and other Structures It contrasts with deconstruction A shipwreck can refer to a wrecked ship or to the event that caused the wreck such as the striking of something that causes the ship to sink the stranding of the ship on rocks Diver training is the process of developing skills and building experience in the use of Diving equipment and techniques so that the diver is able to dive safely and Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. Fish farming is the principal form of Aquaculture, while other methods may fall under Mariculture. The fishing industry includes any industry or activity concerned with taking culturing processing preserving storing transporting marketing or selling fish or fish products 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. Abalone (from Spanish Abulón) are medium-sized to very large edible sea Snails marine Gastropod Mollusks in the Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk. A scallop (ˈskɒləp or /ˈskæləp/ is a marine Bivalve Mollusk of the family Pectinidae. This article is about the animal For the B-52's song see Rock Lobster. The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals A frogman is someone who is trained to dive or swim in a military capacity often in combat Human torpedoes or manned torpedoes were secret naval weapons of World War II. A frogman is someone who is trained to dive or swim in a military capacity often in combat A harbor or harbour (see spelling differences) or haven, is a place where ships may shelter from the Weather or are stored 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, 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

Some professional, commercial, and police diving activities are sometimes performed by volunteer divers. A naval mine is a self-contained Explosive device placed in water to destroy Ships or Submarines Unlike Depth charges mines are deposited Bomb disposal is the process by which hazardous explosive devices are rendered safe Unexploded ordnance (or UXO s/ UXB s sometimes acronymized as UO) are explosive Weapons ( Bombs Bullets shells Underwater photography is the process of taking Photographs while under water Police diving is a branch of Professional diving carried out by Police services For the TV series of this title see Search and Rescue (TV series. Spearfisherman redirects here For the former diving gear company see Spearfisherman (company. Marine biology is the scientific study of living Organisms in the Ocean or other marine or Brackish bodies of water Underwater is a term describing the realm below the surface of Water where the water exists in a natural feature (called a body of water) such as an Ocean Tourism is Travel for Recreational or Leisure purposes The World Tourism Organization defines tourists as people who "travel Underwater archaeology is the study of past Human life behaviours and cultures using the physical remains found in salt or Fresh water or buried beneath A shipwreck can refer to a wrecked ship or to the event that caused the wreck such as the striking of something that causes the ship to sink the stranding of the ship on rocks A harbor or harbour (see spelling differences) or haven, is a place where ships may shelter from the Weather or are stored In Architecture, Construction, Engineering and real estate development the word building may refer to one of the following Any man-made A volunteer is someone who works for a community or for the benefit of environment primarily because they choose to do so

Within recreational diving there are those who are considered professional divers, because they maintain a professional standard of training and skills and may need to carry professional liability insurance. Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. This article is about people called professionals For the Movie, see The Professional or Leon. This article is about people called professionals For the Movie, see The Professional or Leon. Liability insurance is a part of the general Insurance system of Risk financing

Some consider technical diving to be a subset of recreational diving, but others separate it out due to the extensively different training equipment and knowledge needed for technical dives.

Public safety diving and military diving may be classified as commercial diving because they make a living from their pursuit of diving; however, public safety divers (police or rescue) and military divers have a different mission from the typical commercial diver. Police are agents or agencies usually of the executive, empowered to enforce the law and to effect public and social order through the legitimatized use of force Rescue refers to operations that usually involve the saving of Life, or prevention of Injury. Scientific diving is used by marine scientists (including diving marine biologists and underwater archaeologists), as a tool for collecting their research data. Underwater archaeology is the study of past Human life behaviours and cultures using the physical remains found in salt or Fresh water or buried beneath

Physiological issues

Breathing underwater

For more information, see diving regulator. A diving regulator is a Pressure regulator used in a Scuba set that supplies the diver with breathing gas

Water normally contains dissolved oxygen from which fish and other aquatic animals extract all their required oxygen as the water flows past their gills. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two A gill is an anatomical structure found in many aquatic organisms Humans lack gills and do not otherwise have the capacity to breathe underwater unaided by external devices. Underwater is a term describing the realm below the surface of Water where the water exists in a natural feature (called a body of water) such as an Ocean [2]

Early diving experimenters quickly discovered it is not enough simply to supply air in order to breathe comfortably underwater. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five As one descends, in addition to the normal atmospheric pressure, water exerts increasing pressure on the chest and lungs — approximately 1 bar or 14. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. 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 in order to inflate the lungs. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit [2]

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. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such A diving regulator is a Pressure regulator used in a Scuba set that supplies the diver with breathing gas

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. A diving mask is an item of Diving equipment that allows scuba divers, free-divers, and snorkelers to see clearly Underwater. A full-face diving mask is a type of Diving mask that seals the whole of the diver's Face from the water and contains a mouthpiece or Demand valve However, inhaling from a regulator's mouthpiece becomes second nature very quickly. In Breathing sets a mouthpiece is a part that the user grips in his Mouth, to make a watertight seal between the breathing set and his mouth

The "Alpha" or "Alfa" flag - Designates a small vessel engaged in diving operations with restricted maneuverability
The "Alpha" or "Alfa" flag - Designates a small vessel engaged in diving operations with restricted maneuverability[5]

For more information about diving regulators, see Diving regulator. A diving regulator is a Pressure regulator used in a Scuba set that supplies the diver with breathing gas

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. A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. A diving regulator is a Pressure regulator used in a Scuba set that supplies the diver with breathing gas [1] 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. Émile Gagnan (November 1900 – 1979 was a French Engineer and co-inventor (together with Jacques-Yves Cousteau) of the demand-valve used for the first Jacques-Yves Cousteau ( 11 June 1910 – 25 June 1997) was a French naval officer explorer, Ecologist, Aqualung was the original name for the first open-circuit scuba diving equipment, developed by Emile Gagnan and Jacques Cousteau in 1943 The "single-hose" system has significant advantages over the original system.

The diver down flag - Designates a diver is in the water
The diver down flag - Designates a diver is in the water

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. A diving regulator is a Pressure regulator used in a Scuba set that supplies the diver with breathing gas 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

Main article: Rebreathers

Less common, but becoming increasingly available, are closed and semi-closed rebreathers. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas Open-circuit sets vent off all exhaled gases, but rebreathers reprocess each exhaled breath for re-use by removing the carbon dioxide buildup and replacing the oxygen used by the diver. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single 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[1], photography, and other applications. A frogman is someone who is trained to dive or swim in a military capacity often in combat Modern rebreathers are more complex and more expensive than sport open-circuit scuba, and need special training and maintenance to safely use.

Gas mixtures

Main article: Breathing gas

For some diving, gas mixtures other than normal atmospheric air (21% oxygen, 78% nitrogen, 1% other) can be used[1][2], so long as the diver is properly trained in their use. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 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. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person

Several other common gas mixtures are in use, and all need specialized training. Oxygen with helium and a reduced percentage of nitrogen is known as trimix, for example. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14

In cases of technical dives more than one cylinder may be carried, containing a different gas mixture for a distinct phase of the dive, typically designated as Travel, Bottom, and Decompression. Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority These different gas mixtures may be used to extend bottom time, reduce inert gas narcotic effects, and reduce decompression times.

Injuries due to changes in air pressure

For a full list, see Diving hazards and precautions

Divers must avoid injuries caused by changes in air pressure. Divers face specific physical and Health Risks when they go Underwater (e 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 14. A wetsuit is a protective garment used for watersports such as Scuba diving, Surfing, Windsurfing, Kitesurfing, and Triathlon lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Paranasal sinuses are air-filled spaces communicating with the nasal cavity within the bones of the Skull and face 7 pounds-force per square inch (101. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of 3 kPa) at sea level. Pressure injuries are called barotrauma[2] and can be quite painful, in severe cases causing a ruptured eardrum or damage to the sinuses. Barotrauma is physical damage to body tissues caused by a difference in Pressure between an air space inside or beside the body and the surrounding Gas or Liquid 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. Ear clearing or clearing the ears is any of various maneuvers to equalize the pressure in the Middle ear with the outside pressure by letting air enter along the

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.

Effects of breathing high pressure gas

Decompression sickness

Main article: Decompression sickness

The diver must avoid the formation of gas bubbles in the body, called decompression sickness[2] or 'the bends', by releasing the water pressure on the body slowly at the end of the dive and allowing gases trapped in the bloodstream to gradually break solution and leave the body, called "off-gassing. Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person " This is done by making safety stops or decompression stops and ascending slowly using dive computers or decompression tables for guidance. A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from A dive computer or decompression meter is a device used by a scuba diver to measure the time and depth of a dive so that a safe ascent rate can be calculated Dive Tables, Decompression Tables or Tables are printed cards or booklets that allow divers to determine for a particular dive profile and breathing gas Decompression sickness must be treated promptly, typically in a recompression chamber. A recompression chamber is a Pressure vessel used to treat divers suffering from certain Diving disorders such as Decompression sickness. 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. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the First aid is the provision of initial care for an Illness or Injury. [6]

Nitrogen narcosis

Main article: 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. Nitrogen narcosis or inert gas narcosis is a reversible alteration in Consciousness in scuba divers at depth Nitrogen narcosis or inert gas narcosis is a reversible alteration in Consciousness in scuba divers at depth [2] 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 the diver at 66 feet (20 m), or 3 atmospheres of pressure. At 66 feet (20 m), Narcosis manifests itself as slight giddiness. The effects increase drastically with the increase in depth. Jacques Cousteau famously described it as the "rapture of the deep". Jacques-Yves Cousteau ( 11 June 1910 – 25 June 1997) was a French naval officer explorer, Ecologist, 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 prevents narcosis from occurring. See Heliox (cryogenic equipment for another use of the word Heliox Heliox is a Breathing gas composed of a mixture of

Oxygen toxicity

Main article: Oxygen toxicity

Oxygen toxicity occurs when oxygen in the body exceeds a safe "partial pressure" (PPO2). Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused [2] 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. An epileptic seizure is caused by excessive and/or hypersynchronous electrical Neuronal activity and is usually self-limiting Oxygen toxicity is preventable provided one never exceeds the established maximum depth of a given breathing gas. For deep dives, (generally past 130 feet / 39 meters) "hypoxic blends" containing a lower percentage of oxygen than atmospheric air are used. For more information, see Oxygen toxicity. Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused

Refraction and underwater vision

A diver wearing an Ocean Reef full face mask
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 rays bend when they enter from one medium to another of different density. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain Light entering the cornea from water is hardly refracted at all, leaving only the eye's crystalline lens to focus light. The lens is a transparent biconvex structure in the Eye that along with the Cornea, helps to Refract Light to be focused This leads to very severe hypermetropia. Hyperopia, also known as farsightedness or longsightedness, is a Defect of vision caused by an imperfection in the Eye (often when People with severe myopia, therefore, can see better underwater without a mask than normal-sighted people. Myopia (from Greek: μυωπία myopia "near-sightedness" also called near- or short-sightedness, is a refractive defect

Diving masks and diving helmets and fullface masks solve this problem by creating an air space in front of the diver's eyes. A diving mask is an item of Diving equipment that allows scuba divers, free-divers, and snorkelers to see clearly Underwater. Diving helmets are worn by mainly by professional divers engaged in Surface supplied diving. A full-face diving mask is a type of Diving mask that seals the whole of the diver's Face from the water and contains a mouthpiece or Demand valve [1] 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. A refractive error, or refraction error, is an error in the focusing of Light by the Eye and a frequent reason for reduced Visual acuity Light rays bend when they enter from one medium to another of different density. 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. A diving mask is an item of Diving equipment that allows scuba divers, free-divers, and snorkelers to see clearly Underwater.

On rare occasions, commando frogmen use special contact lenses instead, to see underwater without the large glass surface of a diving mask, which can reflect light and give away the frogman's position. A frogman is someone who is trained to dive or swim in a military capacity often in combat A contact lens (also known simply as a contact) is a corrective, cosmetic, or therapeutic lens usually placed on the Cornea

As a diver changes depth, he must periodically exhale through his nose to equalize the internal pressure of the mask with that of the surrounding water. Swimming goggles which only cover the eyes do not allow for equalization and thus are not suitable for diving.

Controlling buoyancy underwater

Diver under the Salt Pier in Bonaire.
Diver under the Salt Pier in Bonaire. In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is The Island Territory of Bonaire ( Dutch: Eilandgebied Bonaire, Papiamento: Teritorio Insular di Boneiru) is one of five island areas

To dive safely, divers need to be able to control their rate of descent and ascent in the water. [2] Ignoring other forces such as water currents and swimming, the diver's overall buoyancy determines whether he ascends or descends. In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is 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. Divers wear weighting systems, weight belts or weights, generally made of Lead, to counteract the Buoyancy of other Diving equipment A diving suit is a garment or device designed to protect a diver from the Underwater environment A wetsuit is a protective garment used for watersports such as Scuba diving, Surfing, Windsurfing, Kitesurfing, and Triathlon A dry suit or drysuit provides Thermal insulation or passive thermal protection to the wearer while immersed in water and is worn by divers, A diving suit is a garment or device designed to protect a diver from the Underwater environment [1] 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 immersed in; if the result is negative, that force is upwards. In the Physical sciences weight is a Measurement of the gravitational Force acting on an object The volume of any solid plasma vacuum or theoretical object is how much three- Dimensional space it occupies often quantified numerically 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 unwanted buoyancy changes. The diver can inject air into some diving suits to counteract this effect and squeeze. Barotrauma is physical damage to body tissues caused by a difference in Pressure between an air space inside or beside the body and the surrounding Gas or Liquid 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. A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving.

Avoiding losing body heat

Water conducts heat from the diver 25 times[7] better than air, which can lead to hypothermia even in mild water temperatures. In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature Hypothermia is a condition in which an organism's temperature drops below that required for normal Metabolism and bodily functions [2] Symptoms of hypothermia include impaired judgment and dexterity[8], 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. The term thermal insulation can refer to materials used to reduce the rate of Heat transfer, or the methods and processes used to reduce heat transfer A wetsuit is a protective garment used for watersports such as Scuba diving, Surfing, Windsurfing, Kitesurfing, and Triathlon A dry suit or drysuit provides Thermal insulation or passive thermal protection to the wearer while immersed in water and is worn by divers, [1]

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. Neoprene or polychloroprene is a family of synthetic Rubbers that are produced by Polymerization of Chloroprene. 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.
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. This article pertains to the chemical element For other uses see Argon (disambiguation.

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:

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. A diving suit is a garment or device designed to protect a diver from the Underwater environment

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. Swimfins, swim fins, fins or flippers are Finlike Rubber or Plastic shoes worn over the foot to aid movement through the A Diver Propulsion Vehicle or a DPV is an item of Diving equipment used by scuba divers to increase their range while underwater where their endurance is Other equipment to improve mobility includes diving bells and diving shots. A diving bell, also known as a wet bell, is a cable-suspended airtight chamber open at the bottom like a Moon pool structure that is lowered Underwater A diving shot is an item of Diving equipment consisting of a Weight, a line and a Buoy.

Scuba dive training and certification agencies

Main article: List of diver training organizations

Recreational scuba diving does not have a centralized certifying or regulatory agency, and is mostly self regulated. This page lists SCUBA Diver training organizations Commercial diving: Surface supplied air training organizations International 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

A scuba diver approaching the "1,000 Steps" dive site in Bonaire.
A scuba diver approaching the "1,000 Steps" dive site in Bonaire. The United States of America —commonly referred to as the The Young Men's Christian Association (" YMCA " or " the Y " was founded on June 6, 1844 in London England by a young man The Island Territory of Bonaire ( Dutch: Eilandgebied Bonaire, Papiamento: Teritorio Insular di Boneiru) is one of five island areas
Scuba diving, grouped
Scuba diving, grouped


Reference List

  1. ^ a b c d e f g h i (2006) US Navy Diving Manual, 6th revision. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. United States: US Naval Sea Systems Command. Retrieved on 2008-04-24. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1479 BC - Thutmose III ascends to the throne of Egypt, although power effectively shifts to Hatshepsut (according to  
  2. ^ a b c d e f g h i j k Brubakk, A. O. ; T. S. Neuman (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. . United States: Saunders Ltd. , 800. ISBN 0702025712.  
  3. ^ Vann RD (2004). "Lambertsen and O2: beginnings of operational physiology". Undersea Hyperb Med 31 (1): 21–31. PMID 15233157.  
  4. ^ Butler FK (2004). "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " "Closed-circuit oxygen diving in the U.S. Navy". Undersea Hyperb Med 31 (1): 3–20. PMID 15233156.  
  5. ^ Rule 27: "Vessel Not Under Command", U. S. Coast Guard, accessed 15 February 2008
  6. ^ Longphre, J. Events 590 - Khosrau II is crowned as king of Persia 1637 - Ferdinand III becomes Holy Roman Emperor 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common M. ; P. J. DeNoble; R. E. Moon; R. D. Vann; J. J. Freiberger (2007). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. "First aid normobaric oxygen for the treatment of recreational diving injuries.". Undersea Hyperb Med. 34 (1): 43-49. ISSN 1066-2936. An International Standard Serial Number ( ISSN) is a unique eight-digit number used to identify a print or electronic Periodical publication. PMID 17393938. OCLC 26915585. The OCLC Online Computer Library Center is according to its website a "nonprofit membership computer library service and research organization dedicated to the public purpose  
  7. ^ "Thermal Conductivity", Georgia State University, accessed 15 February 2008
  8. ^ Weinberg, R. Events 590 - Khosrau II is crowned as king of Persia 1637 - Ferdinand III becomes Holy Roman Emperor 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common P. ; E. D. Thalmann. (1990). Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) "Effects of Hand and Foot Heating on Diver Thermal Balance.". Naval Medical Research Institute Report 90-52.  

Further Reading

External links

Dictionary

scuba diving

-noun

  1. underwater swimming using scuba equipment
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