Underwater diving is the practice of descending below the water's surface to conduct underwater activities. In ambient pressure diving, the diver is exposed to the pressure of the surrounding water, and uses breathing apparatus such as that used for scuba diving or surface supplied diving, or when freediving, will breath-hold for the duration of the dive. The saturation diving technique can be used to reduce the risk of decompression sickness after long duration deep dives. Atmospheric diving suits may be used to isolate the diver from the effects of high ambient pressure. Although not usually considered to be diving, the use of crewed submersibles can extend the range of possible diving depths, and remotely controlled and robotic diving machines can be used where the risks to human divers are unacceptable or the logistics are impractical.
The diving environment exposes the diver to a wide range of hazards, and though the risks are largely controlled by appropriate diving skills, training, types of equipment and breathing gases used depending on the mode, depth and purpose of diving, it remains a relatively dangerous activity. Diving activities are restricted to relatively shallow depths ranging from around 40 m (130 ft.) maximum for recreational Scuba diving to commercial saturation diving maximum around 534 metres (1,752 ft) and 610 metres (2,000 ft) wearing atmospheric diving suits. Diving is also restricted to conditions which are not excessively hazardous, though the level of risk acceptable to the diver can vary considerably. Occasionally diving may be done in liquids other than water.
Recreational diving (also called sport diving or subaquatics) is a popular leisure activity . Technical diving is a form of recreational diving that achieves greater depths or endurance or addresses more challenging conditions than found in normal recreational diving. Professional diving (commercial diving, diving for scientific research purposes or diving for financial gain) takes a range of diving activities to the underwater work site. Public safety diving is the underwater work done by law enforcement, fire rescue, and search & rescue/recovery dive teams, and may be done by professionals or volunteers. Military diving includes combat diving, clearance diving and ship's husbandry diving. Underwater sports is a group of competitive sports using either free-diving, snorkeling or scuba technique, or a combination of these techniques. The term "deep sea diving" refers to underwater diving, usually with surface supplied equipment, and often refers specifically to the use of standard diving dress with the traditional copper helmet. "Hard hat" diving is any form of diving with a helmet, including the standard copper helmet, and other forms of free-flow and lightweight demand helmets.
- 1 Diving modes
- 2 Range of diving activities
- 3 History
- 4 Dive sites
- 5 Underwater divers
- 6 Physiological aspects of diving
- 7 Risks and safety
- 8 Terminology
- 9 Diving by other animals
- 10 See also
- 11 References
- 12 Further reading
- 13 External links
There are several modes of diving based on the diving equipment used.
The ability to dive and swim underwater while holding one's breath is considered a useful emergency skill, an important part of water sport and Navy safety training, and an enjoyable leisure activity. Underwater diving without breathing apparatus can be loosely categorized as underwater swimming, snorkeling and free-diving. These categories overlap considerably. Several competitive underwater sports are practiced without breathing apparatus.
Free-diving does not involve the use of external breathing devices, but relies on the ability to hold one's breath until resurfacing. It includes a range of activities from simple breath-hold diving to competitive apnea dives. Fins and a diving mask are often used in free diving to improve vision and provide more efficient propulsion. A short breathing tube called a snorkel allows the diver to breathe at the surface while the face is immersed. Snorkeling on the surface with no intention of diving is a popular water sport and recreational activity.
Scuba diving is diving with a self-contained underwater breathing apparatus, which is completely independent of surface supply. Scuba provides the diver with the advantages of mobility and horizontal range far beyond the reach of an umbilical hose attached to surface-supplied diving equipment (SSDE). Scuba divers engaged in armed forces covert operations may be referred to as frogmen, combat divers or attack swimmers. There are two main classes of scuba distinguished by how the breathing gas is used:
- Open circuit scuba systems discharge the breathing gas into the environment as it is exhaled, and consist of one or more diving cylinders containing breathing gas at high pressure which is supplied to the diver through a diving regulator. They may include additional cylinders for decompression gas or emergency breathing gas.
- Closed-circuit or semi-closed circuit rebreather scuba systems allow recycling of exhaled gases. The volume of gas used is reduced compared to that of open circuit; therefore, a smaller cylinder or cylinders, may be used for an equivalent dive duration. They far extend the time spent underwater as compared to open circuit for the same gas consumption. Rebreathers produce fewer bubbles and less noise than scuba which makes them attractive to covert military divers to avoid detection, scientific divers to avoid disturbing marine animals, and media divers to avoid bubble interference.
Surface supplied diving
An alternative to self-contained breathing systems is to supply breathing gases from the surface through a hose. When combined with a communication cable, a pneumofathometer line and a safety line, an optional hot water hose for heating, a video cable and a gas reclaim line, it is called the diver's umbilical. More basic equipment that may use only an air hose is called an airline or hookah system.
- Saturation diving lets professional divers live and work under pressure for days or weeks at a time. After working in the water, the divers rest and live in a dry pressurized underwater habitat on the bottom or a saturation life support system of pressure chambers on the deck of a diving support vessel, oil platform or other floating platform at a similar pressure to the work depth. They are transferred between the surface accommodation and the underwater workplace in a pressurised closed diving bell, also known as a personnel transfer capsule. Decompression at the end of the dive may take many days, but since it is done only once for a long period of exposure, rather than after each of many shorter exposures, the overall risk of decompression injury to the diver and the total time spent decompressing are reduced. This type of diving allows greater economy of work and enhanced safety.
- Surface oriented, or bounce diving, is how commercial divers refer to diving operations where the diver starts and finishes the diving operation at atmospheric pressure. The diver may be deployed directly, often from a diving support vessel or indirectly via a diving bell. Surface-supplied divers almost always wear diving helmets or full face diving masks. The bottom gas can be air, nitrox, heliox or trimix, the decompression gases may be similar, or may include pure oxygen. Decompression procedures include in-water decompression or surface decompression in a deck chamber.
- A wet bell with a gas filled dome provides more comfort and control than a stage and allows for longer time in water. Wet bells are used for air and mixed gas, and divers can decompress on oxygen at 12 metres (40 ft). Small closed bell systems have been designed that can be easily mobilized, and include a two-man bell, a handling frame and a chamber for decompression after transfer under pressure (TUP). Divers can breathe air or mixed gas at the bottom but are usually recovered with the chamber filled with air. They decompress on oxygen supplied through built in breathing systems (BIBS) towards the end of the decompression. Small bell systems support bounce diving down to 120 metres (390 ft) and for bottom times up to 2 hours.
- A relatively portable surface gas supply system using high pressure gas cylinders for both primary and reserve gas, but using the full diver's umbilical system with pneumofathometer and voice communication is known in the industry as Scuba replacement.
- Another alternative to scuba diving is "airline" or "hookah" diving which allows the diver to breathe using an air supply hose from a cylinder or compressor at the surface. Breathing gas is supplied through a mouth-held demand valve or light full-face mask. It is used for light work such as hull cleaning and archaeological surveys, for shellfish harvesting, and as "Snuba", which is a shallow water activity typically used by tourists and those who are not scuba-certified.
- Surface-supplied diving#Compressor diving is a rudimentary method of surface-supplied diving used in some tropical regions such as the Philippines and the Caribbean. The divers swim with a half mask and fins and are supplied with air from an industrial low-pressure air compressor on the boat through plastic tubes. There is no reduction valve; the diver holds the hose end in his mouth with no demand valve or mouthpiece and allows excess air to spill out between the lips.
Atmospheric pressure diving
Submersibles and 'hard' atmospheric diving suits enable diving to be carried out in a dry environment at normal atmospheric pressure. An atmospheric diving suit (ADS) is a small one-person articulated submersible of anthropomorphic form which resembles a suit of armour, with elaborate joints to allow articulation while maintaining an internal pressure of one atmosphere. An ADS can be used for deeper dives of up to about 2,300 feet (700 m) for many hours, and eliminates the majority of physiological dangers associated with deep diving; the occupant need not decompress, there is no need for special gas mixtures, and there is no danger of nitrogen narcosis, at the expense of higher cost, complex logistics and loss of dexterity.
Robotic autonomous underwater vehicles and remotely operated underwater vehicles also carry out some functions of divers. They can be deployed at greater depths and in more dangerous environments. An autonomous underwater vehicle (AUV) is a robot which travels underwater without requiring input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater vehicles (ROVs) – controlled and powered from the surface by an operator/pilot via an umbilical or using remote control. In military applications AUVs are more often referred to simply as unmanned undersea vehicles (UUVs).
Range of diving activities
Diving may be done for a number of reasons, both personal and professional. Recreational diving is purely for enjoyment and has a number of specialisations and technical disciplines to provide more scope for varied activities for which specific training can be offered, such as cave diving, wreck diving, ice diving and deep diving.
Competitive underwater sport is also done for enjoyment and includes specific sports such as aquathlon (i.e. underwater wrestling), finswimming, free-diving, spearfishing, sport diving, underwater football, underwater hockey, underwater ice hockey, underwater orienteering, underwater photography, underwater rugby, underwater target shooting and underwater videography. Many of these underwater sports can be enjoyed simply for exercise and the associated health benefits, for true recreation, or competition at varying levels. Recreational diving is generally done using scuba or freediving modes.
There are various aspects of professional diving that range anywhere from part-time work to lifelong careers. Professionals in the recreational dive industry include instructor trainers, dive instructors, assistant instructors, divemasters, dive guides, and scuba technicians. Commercial diving is industry related and includes civil engineering tasks such as in oil exploration, offshore construction dam maintenance and harbour works. 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 aquaculture.
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, 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, paramedical service or lifeguard unit, and may be classed as public safety diving. There are also professional divers such as underwater photographers and videographers, who record the underwater world, and scientific divers in fields of study which involve the underwater environment, including marine biologists, geoligists, hydrologists, oceanographers and underwater archaeologists.
The choice between scuba and surface supplied diving equipment is based on both legal and logistical constraints. Where the diver requires mobility and a large range of movement, scuba is usually the choice if safety and legal constraints allow. Higher risk work, particularly commercial diving, may be restricted to surface supplied equipment by legislation and codes of practice.
The history of underwater diving starts with freediving as a widespread means of hunting and gathering, both for food and other valuable resources such as pearls and coral, from before 4500 BCE. By classical Greek and Roman times commercial applications such as sponge diving and marine salvage were established, Military diving also has a long history, going back at least as far as the Peloponnesian War, with recreational and sporting applications being a recent development. Technological development in ambient pressure diving started with stone weights (skandalopetra) for fast descent. In the 16th and 17th centuries diving bells became functionally useful when a renewable supply of air could be provided to the diver at depth, and progressed to surface supplied diving helmets - in effect miniature diving bells covering the diver's head and supplied with compressed air by manually operated pumps - which were improved by attaching a waterproof suit to the helmet and in the early 19th century became the standard diving dress, which made a far wider range of marine civil engineering and salvage projects practicable.
Limitations in mobility of the surface supplied systems encouraged the development of both open circuit and closed circuit scuba in the 20th century, which allow the diver a much greater autonomy. These also became popular during World War II for clandestine military operations, and post-war for scientific, search and rescue, media diving, recreational and technical diving. The heavy free-flow surface supplied copper helmets evolved into lightweight demand helmets, which are more economical with breathing gas, which is particularly important for deeper dives and expensive helium based breathing mixtures, and saturation diving reduced the risks of decompression sickness for deep and long exposures.:1–9
An alternative approach was the development of the "single atmosphere" or armoured suit, which isolates the diver from the pressure at depth, at the cost of great mechanical complexity and limited dexterity. The technology first became practicable in the middle 20th century. Isolation of the diver from the environment was taken further by the development of remotely operated underwater vehicles in the late 20th century, where the operator controls the ROV from the surface, and autonomous underwater vehicles, which dispense with an operator altogether. All of these modes are still in use and each has a range of applications where it is has advantages over the others, though diving bells have largely been relegated to a means of transport for surface supplied divers. In some cases combinations are particularly effective, such as the simultaneous use of surface orientated or saturation surface supplied diving equipment and work or observation class remotely operated vehicles.
By the late 19th century, as salvage operations became deeper and longer, an unexplained malady began afflicting the divers; they would suffer breathing difficulties, dizziness, joint pain and paralysis, sometimes leading to death. The problem was already well known among workers building tunnels and bridge footings operating under pressure in caissons and was initially called 'caisson disease' but later the 'bends' because the joint pain typically caused the sufferer to stoop. Early reports of the disease had been made at the time of Pasley's salvage operation, but scientists were still ignorant of its causes.
French physiologist Paul Bert was the first to understand it as decompression sickness. His classical work, La Pression barometrique (1878), was a comprehensive investigation into the physiological effects of air-pressure, both above and below the normal. He determined that inhaling pressurized air caused the nitrogen to dissolve into the bloodstream; rapid depressurization would then release the nitrogen into its natural gaseous state, forming bubbles that could block the blood circulation and potentially cause paralysis or death. Central nervous system oxygen toxicity was also first described in this publication and is sometimes referred to as the "Paul Bert effect".
John Scott Haldane designed a decompression chamber in 1907 and he produced the first decompression tables for the Royal Navy in 1908 after extensive experiments with animals and human subjects. These tables established a method of decompression in stages - it remains the basis for decompression methods to this day. Following Haldane's recommendation, the maximum safe operating depth for divers was extended to 200 feet (61 m).:1-1
The US Navy continued its decompression research, and in 1915, the first C & R tables (Bureau of Construction and Repair) were developed by French and Stilson. A significant number of experimental dives were conducted in the 1930s, and formed the basis for the 1937 US Navy air decompression tables. Surface decompression and oxygen use were also researched in the 1930s, and the US Navy 1957 tables developed to deal with problems found in the 1937 tables.
In 1965 Hugh LeMessurier and Brian Andrew Hills published their paper, A thermodynamic approach arising from a study on Torres Strait diving techniques, which suggested that decompression by conventional models results in bubble formation which is then eliminated by re-dissolving at the decompression stops which is slower than off-gassing while still in solution. This indicates the importance of minimizing bubble phase for efficient gas elimination.
M.P. Spencer showed that doppler ultrasonic methods can detect venous bubbles in asymptomatic divers. and Dr Andrew Pilmanis showed that safety stops reduced bubble formation. In 1981 D.E. Yount described the Varying Permeability Model, proposing a mechanism of bubble formation. Several other bubble models followed. Although the pathophysiology of decompression sickness in not yet fully understood, decompression practice has reached a stage where the risk is fairly low, and most incidences are successfully treated by therapeutic recompression and hyperbaric oxygen therapy. Mixed breathing gases are routinely used to reduce the effects of the hyperbaric environment on ambient pressure divers.
The common term for a place at which one may dive is a dive site. As a general rule, professional diving is done where the work needs to be done, and recreational diving is done where conditions are suitable. As a consequence, there are many recorded and publicized recreational dive sites which are known for their convenience, points of interest, and frequently favourable conditions. Diver training facilities for both professional and recreational divers will generally use a small range of dive sites which are familiar, convenient and where conditions are predictable and the risk is relatively low.
Recreational diver service organisations may provide websites or brochures listing the sites to which they provide access, and popular dive sites in many parts of the world have been described in magazines and books in a widely varying range of detail and accuracy. There are also travel and other specialist websites which provide the recreational diver with facilities to describe dive sites, either as blogs or as co-operative travel guides.
Dive sites are restricted by accessibility and risk, but may include water and occasionally other liquids. Most underwater diving is done in the shallower coastal parts of the oceans, and inland bodies of freshwater, including lakes, dams, quarries, rivers, springs, flooded caves, reservoirs, tanks, swimming pools, and canals, but may also be done in large bore ducting and sewers, power station cooling systems, cargo and ballast tanks of ships, and liquid-filled industrial equipment. Diving in liquids other than water may present special problems due to density, viscosity and chemical compatibility of diving equipment, as well as possible environmental hazards to the diving team.
The depth range for human diving operations is small compared with the depth of the sea: The recreational diving depth limit for EN 14153-2 / ISO 24801-2 level 2 "Autonomous Diver" standard is 20 metres (66 ft). The recommended depth limit for more extensively trained recreational divers ranges from 30 metres (98 ft) for PADI divers, (this is the depth at which nitrogen narcosis symptoms generally begin to be noticeable in adults), 40 metres (130 ft) specified by Recreational Scuba Training Council, 50 metres (160 ft) for divers of the British Sub-Aqua Club and Sub-Aqua Association breathing air, and 60 metres (200 ft) for teams of 2 to 3 French Level 3 recreational divers, breathing air.
For technical divers, the recommended maximum depths are greater on the understanding that they will use less narcotic gas mixtures. 100 metres (330 ft) is the maximum depth authorised for divers who have completed Trimix Diver certification with IANTD or Advanced Trimix Diver certification with TDI. 332 metres (1,089 ft) is the world record depth on scuba (2014). Commercial divers using saturation techniques and heliox breathing gases routinely exceed 100 metres (330 ft), but they are also limited by physiological constraints. Comex Hydra 8 experimental dives reached a record open water depth of 534 metres (1,752 ft) in 1988. Atmospheric Diving System (ADS) suits are mainly constrained by the technology of the articulation seals, and have achieved a depth of 610 metres (2,000 ft) by a US Navy diver.
Underwater diver training is normally given by a qualified instructor who is a member of one of many diving training agencies or is registered with a government agency. Basic diver training entails the learning of skills required for the safe conduct of activities in an underwater environment, and includes procedures and skills for the use of diving equipment, safety, emergency self-help and rescue procedures, dive planning, and use of dive tables.
- Equalisation of pressure differentials between the environment and the air spaces of the ear, other air spaces inside the body, and air spaces between diving equipment and the body.
- Underwater breathing – the skill of breathing through the apparatus.
- Mask clearing – the skill of clearing water from the mask.
- Air sharing – assisting another diver by providing air from one's own supply, or receiving air supplied by another diver.
- Emergency ascents - how to return to the surface without injury in the event of a breathing supply interruption.
- Use of bailout systems (professional and technical divers)
- Buoyancy control – correct buoyancy allows the diver to move about underwater safely and comfortably.
- Diving signals – used to communicate underwater. Professional divers will also learn other methods of communication.
Some knowledge of physiology and the physics of diving is considered necessary by most diver certification agencies, as the diving environment is alien and relatively hostile to humans. The physics and physiology knowledge required is fairly basic, and helps the diver to understand the effects of the diving environment so that informed acceptance of the associated risks is possible. The physics mostly relates to gases under pressure, buoyancy, heat loss, and light underwater. The physiology relates the physics to the effects on the human body, to provide a basic understanding of the causes and risks of barotrauma, decompression sickness, gas toxicity, hypothermia, drowning and sensory variations. More advanced training often involves first aid and rescue skills, skills related to specialized diving equipment, and underwater work skills.
Physiological aspects of diving
The physiology of diving and hyperbaric exposure includes the following aspects.
- Physiology of immersion, including cold shock response and the mammalian diving reflex.
- Physiology of decompression
- Acute and chronic dysbaric disorders
- Physiology of hyperbaric oxygen therapy, including oxygen toxicity
- Pressure and inert gas effects, including nitrogen narcosis and high pressure neurological syndrome
Fitness to dive
Medical fitness to dive is the medical and physical suitability of a diver to function safely in the underwater environment using underwater diving equipment and procedures. Depending on the circumstances it may be established by a signed statement by the diver that he or she does not suffer from any of the listed disqualifying conditions and is able to manage the ordinary physical requirements of diving, to a detailed medical examination by a physician registered as a medical examiner of divers following a procedural checklist, and a legal document of fitness to dive issued by the medical examiner.
Diving medicine is the diagnosis, treatment and prevention of conditions caused by exposing divers to the underwater environment. It includes the effects on the body of pressure on gases, the diagnosis and treatment of conditions caused by marine hazards and how fitness to dive affects a diver's safety. Hyperbaric medicine is another field associated with diving, since recompression in a hyperbaric chamber with hyperbaric oxygen therapy is the definitive treatment for two of the most significant diving-related illnesses, decompression sickness and arterial gas embolism.
Diving medicine deals with medical research on issues of diving, the prevention of diving disorders, treatment of diving accident injuries and diving fitness. The field includes the effect of breathing gases and their contaminants under high pressure on the human body and the relationship between the state of physical and psychological health of the diver and safety. In diving accidents it is common for multiple disorders to occur together and interact with each other, both causatively and as complications. Diving medicine is a branch of occupational medicine and sports medicine, and first aid and recognition of symptoms of diving disorders is an important part of diver education.
Risks and safety
Hazard and vulnerability interact with likelihood of occurrence to create risk, which can be the probability of a specific undesirable consequence of a specific hazard, or the combined probability of undesirable consequences of all the hazards of a specific activity. The presence of a combination of several hazards simultaneously is common in diving, and the effect is generally increased risk to the diver, particularly where the occurrence of an incident due to one hazard triggers other hazards with a resulting cascade of incidents. Many diving fatalities are the result of a cascade of incidents overwhelming the diver, who should be able to manage any single reasonably foreseeable incident.
The assessed risk of a dive would generally be considered unacceptable if the diver is not expected to cope with any single reasonably foreseeable incident with a significant probability of occurrence during that dive. Precisely where the line is drawn depends on circumstances. Commercial diving operations are constrained by occupational health and safety legislation, but also by the physical realities of the operating environment, and expensive engineering solutions are often necessary to control risk. A formal hazard identification and risk assessment is a standard and required part of the planning for a commercial diving operation, and this is also the case for offshore diving operations. The occupation is inherently hazardous, and great effort and expense are routinely incurred to keep the risk within an acceptable range. The standard methods of reducing risk are followed where possible.
Statistics on injuries related to commercial diving are normally collected by national regulators. In the UK the Health and Safety Executive (HSE) is responsible for the overview of about 5,000 commercial divers, and in Norway the corresponding authority is the Petroleum Safety Authority Norway (PSA), which has maintained the DSYS database since 1985, gathering statistics on over 50,000 diver-hours of commercial activity per year. The risks of dying during recreational, scientific or commercial diving are small, and on scuba, deaths are usually associated with poor gas management, poor buoyancy control, equipment misuse, entrapment, rough water conditions and pre-existing health problems. Some fatalities are inevitable and caused by unforeseeable situations escalating out of control, but the majority of diving fatalities can be attributed to human error on the part of the victim. According to a North American 1972 analysis of calendar year 1970 data, diving was, based on man hours, 96 times more dangerous than driving an automobile. According to a 2000 Japanese study, every hour of recreational diving is 36 to 62 times riskier than automobile driving.
Scuba diving fatalities have a major financial impact by way of lost income, lost business, insurance premium increases and high litigation costs. Equipment failure is rare in open circuit scuba, and while the cause of death is commonly recorded as drowning, this is usually the consequence of an uncontrollable series of events taking place in water. Air embolism is also frequently cited as a cause of death, and it, too is the consequence of other factors leading to an uncontrolled and badly managed ascent, occasionally aggravated by medical conditions. About a quarter of diving fatalities are associated with cardiac events, mostly in older divers. There is a fairly large body of data on diving fatalities, but in many cases the data is poor due to the standard of investigation and reporting. This hinders research which could improve diver safety.
Artisanal fishermen and gatherers of marine organisms in less developed countries may expose themselves to relatively high risk using diving equipment if they do not understand the physiological hazards, particularly if they use inadequate equipment. 
Divers operate in an environment for which the human body is not well suited. They face specific physical and health risks when they go underwater or use high pressure breathing gas. The consequences of diving incidents range from merely annoying through to rapidly fatal, and the actual result often depends on the equipment, skill, response and fitness of the diver and diving team. The hazards can be listed under several categories:
- The aquatic environment
- Use of breathing equipment in an underwater environment
- Exposure to a pressurised environment and pressure changes, which includes:
- Pressure changes during descent
- Pressure changes during ascent
- Breathing gases at high ambient pressure
- The specific diving environment
- Pre-existing physiological and psychological conditions in the diver
- Diver behaviour and competence
- Failure of diving equipment other than breathing apparatus
- Hazards of the dive task and special equipment
- Hazards related to access to and egress from the water.
The presence of a combination of several hazards simultaneously is common in diving, and the effect is generally increased risk to the diver, particularly where the occurrence of an incident due to one hazard triggers other hazards with a resulting cascade of incidents. Many diving fatalities are the result of a cascade of incidents overwhelming the diver, who should be able to manage any single reasonably foreseeable incident. The assessed risk of a dive would generally be considered unacceptable if the diver is not expected to cope with any single reasonably foreseeable incident with a significant probability of occurrence during that dive. Precisely where the line is drawn depends on circumstances. Commercial diving operations tend to be less tolerant of risk than recreational, particularly technical divers, who are less constrained by occupational health and safety legislation.
Management of risk
Risk is controlled by the usual measures, including hazard identification and risk assessment (HIRA), protective equipment, medical screening, training and standardised procedures. Professional divers are generally legally obliged to formally carry out and record these measures, and though many of them are not legally required of recreational divers, they are generally informally performed by competent recreational divers, and particularly technical divers, and are an important part of their training. For example: medical statement or examination, pre-dive site assessment and briefing, safety drills, equipment redundancy, alternative air source, buddy checks, buddy or team diving procedures, dive planning, underwater hand signals, and carrying first aid and oxygen administration equipment.
Inshore and inland commercial and military diving is directly regulated by legislation in many countries. Responsibility of the employer, client and diving personnel is specified in these cases, while offshore commercial diving may take place in international waters, and is often done following the guidelines of a voluntary membership organisation such as the International Marine Contractors Association (IMCA), which publishes codes of accepted best practice which their member organisations are expected to follow.
Scientific diving may be classed as commercial diving for regulatory purposes, but in some cases, such as in the US it is specifically exempted from the federal regulations governing commercial diving as there is a non-governmental body, the American Academy of Underwater Sciences, which regulates the field.
Recreational diver training, and dive leading are industry regulated in some of those countries, and only directly regulated by government in a subset of them. In the UK, HSE legislation specifically includes recreational diver training and dive leading for reward, while the US and South Africa are examples where industry regulation is accepted, though non-specific health and safety legislation would still apply.
The legal responsibility of recreational diving service providers is usually limited as far as possible by waivers which they require the customer to sign before engaging in any diving activity. The extent of legal responsibility of recreational buddy divers is unclear and has been the subject of considerable litigation. It is probable that it varies between jurisdictions. In spite of this lack of clarity, buddy diving is recommended by recreational diver training agencies as safer than solo diving, and some service providers will insist that customers dive as buddy pairs.
The terminology of diving is influenced by the environment, equipment technology and associated activities. It includes a range of terms seldom used in other contexts, including a range of acronyms, abbreviations and jargon, which can make it tricky for the uninitiated to follow the literature and conversation. The various applications and modes of diving have their own specialised terminology, though there is a large amount of common ground.
Diving by other animals
Humans are not the only air-breathing creatures to dive. Marine mammals such as seals, dolphins and whales, dive to feed and catch prey under the sea as do penguins and many seabirds, as well as various reptiles: turtles, saltwater crocodiles, seasnakes and marine iguanas. Many mammals, birds and reptiles also dive in freshwater rivers and lakes.
- Busuttili, Mike; Holbrook, Mike; Ridley, Gordon; Todd, Mike, eds. (1985). "Using basic equipment". Sport diving - The British Sub-Aqua Club Diving Manual. Sranley Paul & Co Ltd. ISBN 0-09-163831-3.
- "The Sport Committee". Confédération Mondiale des Activités Subaquatiques.
- "About Aquathlon". Confédération Mondiale des Activités Subaquatiques.
- "North Pacific Acoustic Laboratory: Environmental Impact Statement". 1. 2001: 3–45.
- US Navy (2006). US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. Retrieved 15 September 2016.
- Welham, Michael G. (1989). Combat Frogmen. Patrick Stephens. ISBN 978-1-85260-217-8.
- NOAA Diving Manual, 4th Edition CD-ROM prepared and distributed by the National Technical Information Service (NTIS)in partnership with NOAA and Best Publishing Company
- Staff. "Guidelines to activity report for diving operations on the norwegian continental shelf". Petroleum Safety Authority Norway.
- Imbert, Jean Pierre (February 2006). Lang and Smith, eds. "Commercial Diving: 90m Operational Aspects" (PDF). Advanced Scientific Diving Workshop. Smithsonian Institution. Retrieved 30 June 2012.
- Staff (February 2014). "IMCA International Code of Practice for Offshore Diving" (PDF). IMCA D 014 Rev. 2. International Marine Contractor's Association. Retrieved 22 July 2016.
- "Lifestyle: SNUBA and the Tourism Industry" (PDF). SNUBA International Inc. 2012. Retrieved 28 September 2016.
- Eleftheriou, Anastasios (2013). Methods for the Study of Marine Benthos (4th ed.). John Wiley & Sons. ISBN 978-1-118-54237-8.
- Oceans: Into the Blue. Episode 1 of the BBC television series Human Planet.
- Thornton, Mike; Randall, Robert E.; Albaugh, E. Kurt (1 January 2001). "Subsea Technology: Atmospheric diving suits bridge gap between saturation diving and ROV units". Offshore Magazine. Tulsa, OK: PennWell Corporation. Retrieved 24 September 2016.
- Thornton, Michael Albert (2000-12-01). "A Survey and Engineering design of atmospheric diving suits" (PDF). Monterey, California: Calhoun: The NPS Institutional Archive. Retrieved 28 September 2016.
- Staff. "ROV Categories - Summary". ROVs. Marine Technology Society. Retrieved 16 September 2016.
- Staff (3 June 2009). "Robot sub reaches deepest ocean". BBC News. BBC. Retrieved 16 September 2016.
- Staff (2013). "Technical Diving". NOAA. Retrieved 17 September 2016.
- Richardson, D (1999). "A brief history of recreational diving in the United States". South Pacific Underwater Medicine Society Journal. 29 (3). ISSN 0813-1988. OCLC 16986801. Retrieved 17 September 2016.
- Staff. "Commercial Diving Operations (1910.401) - Scope and application". Occupational Safety and Health Standards subpart T. United States Department of Labor Occupational Safety and Health Administration. Retrieved 17 September 2016.
- Staff (2016). "Work activities". Job profiles: Diver. National Careers Service. Retrieved 17 September 2016.
- Staff (2016). "What does a Commercial Diver do?". Vancouver, Canada: Sokanu. Retrieved 17 September 2016.
- Blades Robinson, (11 January 2002). What is public safety diving, http://www.sandiegodiving.com/education/items/9.html , accessed 17 September 2016
- Phillips, Mark (November 2015). "Public Safety Diving and OSHA, Are We Exempt? Final Answer." (PDF). PS Diver Magazine. Mark Phillips. Retrieved 7 June 2016.
- Staff. "Code Of Practice for Scientific Diving". Pretoria: The South African Department of Labour.
- Diving Regulations 2009 of the South African Occupational Health and Safety Act, 1993. Government notice R41, Government Gazette #32907 of 29 January 2010, Government Printer, Pretoria
- Staff. "Code Of Practice Inshore Diving". Pretoria: The South African Department of Labour.
- Edmonds, C; Lowry, C; Pennefather, J (1975). "History of diving". Journal of the South Pacific Underwater Medicine Society (Reprinted from 'Diving and Subaquatic Medicine'). Retrieved 20 September 2016.
- Sandra Hendrikse & André Merks (12 May 2009). "Diving the Skafandro suit". Diving Heritage. Retrieved 2016-09-18.
- Thucydides (431 BCE). History of the Peloponnesian War.
- Slight, Julian; Durham, Sir Philip Charles Henderson (1843). A narrative of the loss of the Royal George at Spithead, August 1782 including Tracey's attempt to raise her in 1782 and Col. Pasley's operations in removing the wreck (9 ed.). S Horsey.
- Broadwater, John D. (2002). "Digging Deeper - Deepwater Archaeology and the Monitor National Marine Sanctuary". International Handbook of Underwater Archaeology. The Springer Series in Underwater Archaeology. US: Springer US. pp. 639–666. doi:10.1007/978-1-4615-0535-8_38. ISBN 978-1-4613-5120-7.
- Acott, C (1999). "A brief history of diving and decompression illness.". South Pacific Underwater Medicine Society Journal. 29 (2). ISSN 0813-1988. OCLC 16986801. Retrieved 17 March 2009.
- "History: Edmond Halley". London Diving Chamber. Retrieved 2006-12-06.
- Davis, RH (1955). Deep Diving and Submarine Operations (6th ed.). Tolworth, Surbiton, Surrey: Siebe Gorman & Company Ltd. p. 693.
- The Infernal Diver by John Bevan, Hardcover - 314 pages (27 May 1996), Submex Ltd; ISBN 0-9508242-1-6
- Dekker, David L. "1860. Benoit Rouquayrol - Auguste Denayrouze". Chronology of Diving in Holland. www.divinghelmet.nl. Retrieved 17 September 2016.
- Staff (1997). "What is a "Rebreather"?". Closed circuit rebreathers. Hawaii: Bishop Museum. Retrieved 17 September 2016.
- Dibiza, Luca. "A little bit of history on ... The scaphandre autonome or The Self Contained Underwater Breathing Apparatus (SCUBA)". Luca Dibiza. Retrieved 17 September 2016.
- Quick, D. (1970). "A History Of Closed Circuit Oxygen Underwater Breathing Apparatus". Royal Australian Navy, School of Underwater Medicine. RANSUM-1-70. Retrieved 3 March 2009.
- Shilling, Charles (1983). "Papa Topside". Pressure, newsletter of the Undersea and Hyperbaric Medical Society. 12 (1): 1–2. ISSN 0889-0242.
- Kindwall, Eric P. "A short history of diving and diving medicine.". In: Bove, Alfred A; Davis, Jefferson C. Diving Medicine. 2nd edition. WB Saunders Company.: 6–7. ISBN 0-7216-2934-2.
- Miller, James W; Koblick, Ian G (1984). Living and working in the sea. Best Publishing Company. p. 432. ISBN 1-886699-01-1.
- Behnke, Albert R (1942). "Effects of High Pressures; Prevention and Treatment of Compressed-air illness". Medical Clinics of North America. 26: 1212–1237.
- "The Carmagnolle Brothers Armoured Dress". Historical Diving Times (37). Autumn 2005.
- "Historique" (in French). Association Les Pieds Lourds. Retrieved 6 April 2015.
- Stewart, Joseph (2011). "Joseph Salim Peress - 1922". Exploring the History of Hyperbaric Chambers, Atmospheric Diving Suits and Manned Submersibles: the Scientists and Machinery. Xlibris Corporation. ISBN 978-1-4568-5724-0.
- Bert, Paul (1943) [First published in French in 1878]. Barometric pressure: Researches in Experimental Physiology. Columbus, OH: College Book Company. Translated by: Hitchcock, Mary Alice; Hitchcock, Fred A.
- Acott, Chris (1999). "Oxygen toxicity: A brief history of oxygen in diving". South Pacific Underwater Medicine Society Journal. 29 (3): 150–5. ISSN 0813-1988. OCLC 16986801. Retrieved 16 October 2011.
- Acott, C. (1999). "JS Haldane, JBS Haldane, L Hill, and A Siebe: A brief resume of their lives.". South Pacific Underwater Medicine Society Journal. 29 (3). ISSN 0813-1988. OCLC 16986801. Retrieved 13 July 2008.
- Boycott, A. E.; G. C. C. Damant; J. S. Haldane (1908). "Prevention of compressed air illness". J. Hygiene. 8 (03): 342–443. doi:10.1017/S0022172400003399. PMC . PMID 20474365. Retrieved 6 August 2008.
- Hellemans, Alexander; Bunch, Bryan (1988). The Timetables of Science. Simon & Schuster. p. 411. ISBN 0671621300.
- C.B. Carlston; R.A. Mathias; C.W. Shilling (6 December 2012). The Physician’s Guide to Diving Medicine. Springer Science & Business Media. p. 237. ISBN 978-1-4613-2671-7.
- Huggins, Karl E. (1992). "Dynamics of decompression workshop". Course taught at the University of Michigan.
- LeMessurier and Hills. (1965) Decompression Sickness. A thermodynamic approach arising from a study on Torres Strait diving techniques. Hvalradets Skrifter, Nr. 48, 54–84.
- Hills, BA (1978). "A fundamental approach to the prevention of decompression sickness". South Pacific Underwater Medicine Society Journal. 8 (2). Retrieved 10 January 2012.
- Spencer MP (February 1976). "Decompression limits for compressed air determined by ultrasonically detected blood bubbles". Journal of Applied Physiology. 40 (2): 229–35. PMID 1249001. Retrieved 10 January 2012.
- Yount, DE (1981). "Application of bubble formation model to decompression sickness in fingerling salmon". Underwater Biomedical Research. Undersea and Hyperbaric Medical Society, Inc. PMID 7324253. Retrieved 4 March 2016.
- Wienke, Bruce R; O'Leary, Timothy R (13 February 2002). "Reduced gradient bubble model: Diving algorithm, basis and comparisons" (PDF). Tampa, Florida: NAUI Technical Diving Operations. Retrieved 25 January 2012.
- Imbert, JP; Paris, D; Hugon, J (2004). "The Arterial Bubble Model for Decompression Tables Calculations" (PDF). EUBS 2004. France: Divetech. Retrieved 27 September 2016.
- Chief Inspector, South African Department of Labour, (2007) Code of Practice for Commercial Diver Training, Revision 3, Pretoria.
- Wikivoyage article on Scuba diving has links to crowdsourced articles on a large number of dive sites throughout the world
- Steven Barsky (2007); Diving in High-Risk Environments, 4th edition, Hammerhead Press, Ventura, CA, ISBN 978-0-9674305-7-7
- Staff. "Competencies of a recreational scuba diver at level 2 "Autonomous Diver"". EUF Certification International. Retrieved 29 September 2013.
- Brylske, A. (2006). Encyclopedia of Recreational Diving, 3rd edition. United States: PADI. ISBN 1-878663-01-1.
- Cole, Bob (March 2008). "Appendix 6". The SAA Buhlmann Deep-stop System Handbook. Sub-Aqua Association. pp. vi–1. ISBN 0-9532904-8-4.
- "Code du Sport, Dispositions relatives aux établissements organisant la pratique de la plongée subaquatique à l'air". Retrieved 15 July 2015.
- TDI Advanced Trimix Diver | SDI | TDI | ERDI
- Liang, John (19 September 2014). "Ahmed Gabr Breaks Scuba Diving World Record". DeeperBlue.com. Retrieved 19 September 2014.
- "Ahmed Gabr breaks record for deepest SCUBA dive at more than 1,000 feet". Guinness World Records. Retrieved 21 January 2015.
- Extreme Environment Engineering Departement Hyperbaric Experimental Centre - History at the Wayback Machine (archived October 5, 2008)
- Navy diver sets world record
- Staff (2016). "Hardsuit depth record". Nuytco Research Ltd. Retrieved 24 September 2016.
- Staff. "Standards for Training Organisations/System". EUF Certification International. Retrieved 28 September 2013.
- Staff, IDSA,(2009), International Diver Training Certification: Diver Training Standards, Revision 4, October 2009 http://www.idsaworldwide.org/docs/diverts0909.pdf Accessed 13 September 2013
- Educational and Training Standards for Physicians in Diving and Hyperbaric Medicine (PDF), Joint Educational Subcommittee of the European Committee for Hyperbaric Medicine (ECHM) and the European Diving Technical Committee (EDTC), 2011, retrieved 30 March 2013
- Williams, G. Elliott, DH. Walker, R. Gorman, DF. Haller, V. Fitness to dive: Panel discussion with audience participation. SPUMS 2001 Volume 31 Number 3. Journal of the South Pacific Underwater Medicine Society http://archive.rubicon-foundation.org/7739 accessdate 7 April 2014
- Bove, Alfred A. (April 2013). "Decompression sickness". MSD Manual, Professional version. Merck. Retrieved 15 September 2015.
- Michael A. Blumenberg, 1996, Human Factors in Diving, Marine Technology & Management Group, University of California, Berkeley. http://archive.rubicon-foundation.org/6474
- Gareth Lock, 2011, Human factors within sport diving incidents and accidents: An Application of the Human Factors Analysis and Classification System (HFACS), http://www.cognitas.org.uk.
- Steven Barsky and Tom Neuman, (2003); Investigating Recreational and Commercial Diving Accidents, Hammerhead Press, Santa Barbara, CA. ISBN 0-9674305-3-4
- Statutory Instruments 1997 No. 2776 Health and Safety, The Diving at Work Regulations 1997, http://www.legislation.gov.uk/uksi/1997/2776/contents/made
- "Diving & Life Support Services" (PDF). QinetiQ. January 2013. Retrieved 16 July 2016.
- "Norway: New Report on Diving Related Accidents Launched". Business guide. Offshore Energy Today. 8 March 2011. Retrieved 16 July 2016.
- Concannon, David G. (2011). Vann, RD; Lang, MA, eds. Legal Issues Associated with Diving Fatalities: Panel Discussion (PDF). Proceedings of the Divers Alert Network 2010 April 8–10 Workshop. Durham, N.C.: Divers Alert Network. ISBN 978-0-615-54812-8. Retrieved 24 May 2016.
- Lansche, James M (1972). "Deaths During Skin and Scuba Diving in California in 1970". California Medicine. 116 (6): 18–22. PMC . PMID 5031739.
- Ikeda, T; Ashida, H (2000). "Is recreational diving safe?". Undersea and Hyperbaric Medical Society. Retrieved 8 August 2009.
- Ange, Michael (Summer 2010). "The 2010 DAN Diving Fatalities Workshop". Alert Diver Online. Divers Alert Network. Retrieved 24 May 2016.
- Caruso, James (2011). Vann, RD; Lang, MA, eds. The Forensic Investigation of Recreational Diving Fatalities (PDF). Proceedings of the Divers Alert Network 2010 April 8–10 Workshop. Durham, N.C.: Divers Alert Network. ISBN 978-0-615-54812-8. Retrieved 24 May 2016.
- Westin, A.A; Asvall, J; Idrovo, G.; Denoble, P.; Brubakk, A.O. (2005). "Diving behaviour and decompression sickness among Galapagos underwater harvesters." (PDF). Undersea and Hyperbaric Medicine. Undersea and Hyperbaric Medical Society, Inc. pp. 175–184. Retrieved 28 September 2016.
- Thomas, Edwin. "What Are the Dangers of Scuba Diving?". Retrieved 17 September 2016.
- Staff. "General hazards - Diving Information Sheet No 1" (PDF). HSE information sheet. Health and Safety Executive. Retrieved 17 September 2016.
- Staff. "Hazards and Solutions". Washington, DC: Occupational Safety and Health Administration. Retrieved 17 September 2016.
- Staff. "Welcome to IMCA". About IMCA. London, UK: International Marine Contractors Association. Retrieved 29 September 2016.
- Staff (2013). "Standards For Scientific Diving". Dauphin Island, AL: The American Academy of Underwater Sciences. Retrieved 29 September 2016.
- AAUS. "A brief history of the AAUS exemption". Retrieved 29 September 2016.
- Coleman, Phyllis; "Scuba diving buddies: rights, obligations, and liabilities", Nova Southeastern University Shepard Broad Law Center, 2007, link: http://www.ssrn.com/abstract=1266346
- Halstead, B (2000). "Line dancing and the buddy system. reprinted with permission from Dive Log 1999; 132(July): 52-54". South Pacific Underwater Medicine Society Journal. 30 (1). ISSN 0813-1988. OCLC 16986801. Retrieved 6 October 2016.
- Powell, Mark (October 2011). "Solo Diving—Coming out of the Closet". Seminar: Dive 2011 Birmingham,. Dive-Tech. Retrieved 6 October 2016.
- Courtney, Wrolf; Faust, Jan. "Scuba slang and technical terms". Retrieved 7 October 2016.
- Staff (2 December 2015). "Glossary of SCUBA Diving, Ocean and Marine Life Terminology". SCUBA travel. Retrieved 7 October 2016.
- Staff (2016). "Glossary of Scuba Diving Terms". Diving Terminology. ScubaEngineer. Retrieved 7 October 2016.
- Staff (1987). "A Handbook of Terminology for the use of Divers and Inspectors on Offshore Structures" (PDF). Offshore Technology Report OTH 87 277. London: Health and Safety Executive. Retrieved 7 October 2016.
- Staff (2008). "Abbrevations and definitions" (PDF). Diving Recommended Practice. Report 411. London and Brussels: International Association of Oil & Gas Producers. pp. 42–43. Retrieved 7 October 2016.
- Gibson, Victor (May 2009). "Glossary of terms". www.shipsandoil.com. Retrieved 7 October 2016.
- Staff (September 30, 2016). "IMCA publishes diving terms document". Publications. Offshore Shipping Online. Retrieved 7 October 2016.
- Staff (August 2016). "ADCI /IOGP /IMCA Diving Terms" (PDF). IMCA D 057. International Marine Contractors Association. Retrieved 7 October 2016.
- Here  you can see Underwater divers and turtles near Sipadan. It was filmed by Christoph Brüx
- "Diving Physiology of Marine Mammals" (PDF). Retrieved 17 September 2016.
- Palmer, Jane (2015-01-15). "Secrets of the animals that dive deep into the ocean". BBC Earth. BBC. Retrieved 17 September 2016.
- Cousteau J.Y. (1953) Le Monde du Silence, translated as The Silent World, Hamish Hamilton Ltd., London; ASIN B000QRK890
- Lang M.A. & Brubakk A.O. (eds., 2009) The Future of Diving: 100 Years of Haldane and Beyond, Smithsonian Institution Scholarly Press, Washington DC
Media related to Underwater diving at Wikimedia Commons