This is a glossary of technical terms, jargon, diver slang and acronyms used in underwater diving. The definitions listed are in the context of underwater diving. There may be other meanings in other contexts.
Underwater diving can be described as a human activity – intentional, purposive, conscious and subjectively meaningful sequence of actions. Underwater diving is practiced as part of an occupation, or for recreation, where the practitioner submerges below the surface of the water or other liquid for a period which may range between seconds to the order of a day at a time, either exposed to the ambient pressure or isolated by a pressure resistant suit, to interact with the underwater environment for pleasure, competitive sport, or as a means to reach a work site for profit, as a public service, or in the pursuit of knowledge, and may use no equipment at all, or a wide range of equipment which may include breathing apparatus, environmental protective clothing, aids to vision, communication, propulsion, maneuverability, buoyancy and safety equipment, and tools for the task at hand.
Many of the terms are in general use by English speaking divers from many parts of the world, both amateur and professional, and using any of the modes of diving. Others are more specialised, variable by location, mode, or professional environment. There are instances where a term may have more than one meaning depending on context, and others where several terms refer to the same concept, or there are variations in spelling. A few are loan-words from other languages.
There are five sub-glossaries, listed here. The tables of content should link between them automatically:
Contents: Top |
Subsection: Top, Da, De, Di, Do, Du
See: Dalton's law
Gas law describing the relation of component pressures of gases in a mixture to the total pressure.[1]See: Divers Alert Network
Also: "manual CCR" (mCCR)
Diver-controlled closed-circuit rebreather. A closed circuit rebreather which requires the diver to monitor oxygen levels and manually inject oxygen or diluent as needed to maintain an appropriate partial pressure in the loop.Main article: DRDC Toronto
Defence and Civil Institute of Environmental Medicine (Toronto, Canada).See: History of decompression research and development#DCIEM model and tables
Decompression tables based on the Kidd-Stubbs model, developed and published by the Defence and Civil Institute of Environmental Medicine.Subsection: Top, Da, De, Di, Do, Du
See: Lifting bag#Breakout
A heavy weight used to control the rise of a lifting bag after breakout, or to capsize it to prevent a runaway lift. Sometimes just called a deadweight. More generally, an anchor that relies on its weight to provide resistance to drag or lift loads. Deadman anchor more generally refers to a buried log, and may be misused in this context, but it is a common term in commercial diving.Also: transfill
To transfer gas between cylinders by differential pressure. No energy is input, flow will stop when valve is closed on reaching target pressure, or pressures are equalised.See: Deck decompression chamber
A twin-lock hyperbaric chamber suitable for surface decompression and emergency recompression. Large enough to hold at least two occupants, one of them lying down.[3]Main article: Decompression (diving)
Reduction in ambient pressure experienced by the diver during the ascent at the end of a dive or hyperbaric exposure, and the process of allowing dissolved inert gases to be eliminated from the body tissues during this reduction in pressure.[4]See: Decompression practice#Decompression algorithms
Specified step-by step procedures used to calculate the decompression stops needed for a given dive profile. The algorithm can be used to generate decompression schedules for a particular dive profile, decompression tables for more general use, or be implemented in dive computer software to perform real-time analysis of decompression status of the diver.[5]See: DSMB
See: Diving chamber#Decompression chamber
Hyperbaric chamber used for decompressing divers and emergency therapeutic recompression.[6]See: dive computer
See: Decompression practice#Accelerated decompression
Gas breathed during decompression. Commonly implies a composition chosen to accelerate decompression by using an increased oxygen content.[6]Main article: Decompression illness
Illness caused by decompression. Includes decompression sickness and arterial gas embolism due to lung overexpansion injury.[7]See: Decompression theory
A conceptual explanation for the physiological effects of decompression and an associated mathematical approximation, usually expressed as an algorithm or formula, which describes and predicts those physiological effects. Some are more reliable than others. None are a true description of the physiological processes, but they may be sufficiently reliable to be useful.See: Decompression practice#Decompression schedule
A specific ascent rate and series of increasingly shallower decompression stops that a diver uses to allow inert gases to be eliminated from the body tissues during ascent after a specific hyperbaric exposure, to reduce the risk of decompression sickness.[6]Main article: Decompression sickness
Also: "the bends", "caisson disease", "DCS", or "divers' disease"
A condition arising from dissolved inert gases coming out of solution during decompression as bubbles in the tissues, organs and blood vessels of the body causing symptoms ranging from rashes to death.[6]See: Decompression practice#Decompression stops
A pause during the ascent phase of a dive that a diver spends at a constant relatively shallow depth to allow safe release of inert gases from the body tissues to avoid decompression sickness.[6]See: Decompression stress
An indicator of risk for decompression sickness associated with the excess (supersaturation) of inert gas dissolved in the various tissues throughout the body, driving bubble formation and growth. Decompression stress can occur without symptomatic decompression sickness, but decompression sickness is a consequence of a high decompression stress.[8][9]See: Decompression practice#Decompression tables
Printed cards or booklets that allow divers to determine a decompression schedule for a particular dive profile and breathing gas.[6]Also: "decompression bar"
See: Decompression practice#Decompression trapezes
A horizontal bar or bars suspended at the depth of intended decompression stops by buoys, used to make decompression stops more comfortable and more secure and provide the divers' surface cover with a visual reference for the divers' position.[10]See: Decompression theory#Thermodynamic model and deep stops
Decompression stops which are deeper than the deepest stops required by decompression algorithms using dissolved phase models.Main article: Dehydration
A condition where the water content of the body is reduced.See: Diving regulator#Demand valve
Mechanism for providing the user with breathing gas flow only when required. The valve may be triggered by a reduction of pressure across the actuator diaphragm to below ambient due to inhalation, or by pressing a manual override (Purge button).[14]See: Depth gauge
A pressure gauge calibrated to measure depth as a function of ambient pressure.See also: jackstay, downline and shotline
A substantial heavily weighted line attached to a secure point at the surface, such as a boat or buoy, which can be used by a diver to control position and depth during descent an ascent.[16]See: Diving cylinder#Developed pressure
The pressure of the compressed gas in a cylinder at a temperature other than the nominal temperature at which charging pressure is specified. Usually refers to pressure when fully charged at a variation from the reference temperature.[17]See: Differential Global Positioning System
An enhancement to Global Positioning System that provides improved location accuracy. DGPS uses a network of fixed, ground-based reference stations to broadcast the difference between the positions indicated by the satellite systems and the known fixed positions.[18]Subsection: Top, Da, De, Di, Do, Du
Main article: Diamond Reef System
A diving skills program that uses a set of standardized portable obstacles to train and evaluate buoyancy skills and educate scuba divers on how to interact with coral reefs.[19]See: Diving hazards#Localised pressure differentials
Situation where water flows from a region of higher pressure to one of lower pressure, and where obstructing the flow will induce a large force on the obstruction. A type of diving hazard.[20]Main article: Decompression theory#Diffusion limited tissues and the "Tissue slab", and series models
Decompression hypothesis that the uptake and elimination of inert gas is limited by diffusion rates in the tissues. Compare with perfusion limited.Also: "dil"
Gas mixture used to dilute the oxygen in the loop of a closed circuit rebreather to a partial pressure suited to the depth.Also: "flush", "dil flush", "loop flush"
See Rebreather diving#Diluent flush
Replacing the gas within the breathing loop of a rebreather by injecting diluent gas while venting the previous gas mix. Usually done to get a breathable mixture of known composition in the loop to check calibration of the oxygen cells.[21]Also: "DIN valve", "DIN regulator", "DIN thread"
Usually refers to G5/8" x 14 tpi[22] parallel thread fittings used to connect a cylinder valve to a filling connection or regulator first stage. Available in 200 bar and 300 bar versions which should only be inter-connectable in safe combinations. 232 bar DIN (5-thread, G5/8) Outlet/Connector #13 to DIN 477 part 1, and 300 bar DIN (7-thread, G5/8) Outlet/Connector #56 to DIN 477 part 5 - these are similar to 5-thread DIN fitting but are rated to 300 bar working pressures. The 300 bar pressures are common in European diving and in US cave diving.[23]See: Diving cylinder#Connection to the regulator
Screw in adapter which can be used with many recent 200/240 bar DIN cylinder valves to allow connection of Yoke regulators or filling whips.Also: anti-debris tube, valve snorkel
See: Scuba cylinder valve#Dip tube
A short tube screwed into the hole in the bottom of the cylinder valve body, which projects into the cylinder internal space. Its function is to prevent any loose debris inside the cylinder from getting into the outlet passages if the cylinder is inverted in use.[14][25]See: Doing It Right
Also: "DIVA"
Display integrated vibrating alarm – A head-up display module which produces a warning vibration to draw the attention of the diver, generally mounted on the diver's mask or the rebreather mouthpiece.[21]Also: "penetration line" "cave line", or "guideline"
Main article Distance line
A line used by scuba divers as a means of returning to a safe starting point in conditions of low visibility, water currents or where pilotage is difficult. They are often used in cave diving and wreck diving where the diver must return to open water after a penetration when it may be difficult to discern the return route.[26][27] Guide lines are also useful in the event of silt out.[28]Also: shed
Disconnect and drop, unceremoniously or hastily abandon.Also: "decompression computer"
Main article: Dive computer
A device used by a scuba diver to measure the time and depth of a dive so that a safe ascent profile can be calculated and displayed so that the diver can avoid decompression sickness.[30]See also: Scuba gas planning#Respiratory minute volume
Factor used in gas consumption estimates which allows for increased breathing rate due to conditions other than depth. Values range from 1.1 for relaxed, stress free conditions to more than 3.0 for heavy work.[31]Main article: Divemaster
A professional level recreational diver who leads a group of less experienced or visiting divers underwater.Main article: Dive profile
The variation of depth with elapsed time during a dive, often depicted as a graph.Main article: Dive site
The place at which the dive occurs. Also, more broadly, a place at which diving occurs, has occurred, or is planned to occur, and the general locality, with extent depending on context. Professional divers may also refer to a work site, or search area if relevant.See: decompression tables
See: Dive timer
An automatically operated electronic timer which records the elapsed time from the start of a dive.See also: Training manual, Diving manual
A publication containing instructional material for diver training. This may relate to a specific certification or a range of certifications, and is usually published either by a certification agency or a diving school for their own use, but may also be published and sold for general consumption.See also: umbilical cable
Bundle of life-support hoses, communication cable, pneumofathomer hose and strength member between the surface control point and a surface-supplied diver.Also: "DAN"
Main article Divers Alert Network
A non-profit organization for assisting divers in medical and travel emergencies, advising divers on medical matters, and medical research on recreational diving safety.Also: "dive tender" and "line attendant"[36]
A person who assists the working diver to prepare for a dive, get in and out of the water, and to undress from the diving equipment, and who tends the lifeline or umbilical while the diver is in the water.[36]Also: wrist slate
See also: wet notes
Piece of opaque white or pale coloured rigid plastic sheet with matte finish that is easily marked with a graphite pencil, used for taking notes, making sketches and written communication underwater.See: Rebreather#Dive/Surface valve
Valve on the mouthpiece of a rebreather which can be switched between the loop and ambient air at the surface. It seals the breathing loop on the surface setting to prevent flooding the loop and is used for this purpose if the mouthpiece is removed from the mouth in the water. Compare with bailout valve (BOV).Main article: Diving bell
A rigid chamber suspended from a cable and used to transport divers to depth and back to the surface.See also: overweighting
Practice of carrying significantly more ballast weight than necessary to neutralise buoyancy. Common in professional diving operations where the diver needs to remain in firm contact with the bottom to work effectively, and is tethered by a lifeline or umbilical to a control point at a place of safety, which is managed by a tender.Also: "DMAC"
Main article Diving Medical Advisory Council
An independent body of diving medical specialists from Northern Europe which provides advice about medical and certain safety aspects of commercial diving.[37]Also: "DMT"
A paramedic specialising in diving related conditions, and medically fit to dive in a hyperbaric chamber.See: Diving mode
The combination of diving equipment, breathing medium and compression/decompression used for a diving operation, e.g. breathhold, open circuit scuba, nitrox rebreather, surface-supplied air, heliox saturation, etc.[20]Main article: Diving operation
A portion of a diving project that can be safely supervised by one person, which can be a single dive or a number of dives.[20]See: regulator
Main article: Diving reflex
The involuntary physiological response to immersion which exists in all air-breathing vertebrates. It is a series of autonomic responses to apnea which are strengthened by facial cooling and hypoxia. It consists of peripheral vasoconstriction and associated hypertension, vagally induced bradycardia and reduction of cardiac output. This appears to preferentially supply oxygen to the brain. Another aspect is splenic contraction which increases haemoglobin content of the blood.[38]Main article: Diving safety officer
The person who administers a United States university's research diving safety program.[39]Main article: Diver communications
Hand sign and light sign system used by scuba divers to communicate when underwater.Also: "basket"
See: Decompression practice#Diving stages and wet bells
A platform on which a diver stands which is hoisted into the water, lowered to the workplace at the bottom, and then hoisted up again to return the diver to the surface and lift them out of the water. The diving stage is particularly effective for controlling rate of descent and ascent.[36]Main article: Diving supervisor
Person in charge of, and responsible for safety of a commercial diving operation. Usually trained, assessed as competent, certified and registered. Formally appointed by the diving contractor.[4]Also: "DSV"
Main article: Diving support vessel
A ship or boat used as a base for diving operations, particularly if designed or fitted out for that purpose.Subsection: Top, Da, De, Di, Do, Du
Also: "DIR"
See: Doing It Right
A holistic philosophy of scuba diving, which encompasses several essential elements, including fundamental diving skills, teamwork, physical fitness, strictly defined standard procedures, and the use of standardised, streamlined and minimalistic equipment configurations.[41]See: Decompression theory#Doppler ultrasonic bubble detection
Ultrasonic signals reflected from bubble surfaces to identify and quantify gas bubbles present in venous blood.Also: "line arrow"
Triangular plastic line marker with two slots which is mounted on a cave guide line to indicate the direction of the exit.[1]Main article: drift diving
Any dive where the diver is transported significantly by drifting with currents during the dive.[41]See: stage cylinder
Main article: Drowning
The process of experiencing respiratory impairment from submersion/immersion in liquid.Main article: Dry bag
Bag which seals in a watertight manner. Used for keeping clothes and other equipment dry in a wet environment.See: closed bell
See: Diving cylinder#Temperature change during filling
Filling scuba cylinders without the use of a water bath for cooling.[44]Main article: Dry suit
A watertight suit worn to keep the diver dry and to provide protection from the environment. Thermal insulation may be provided by the suit or garments worn under the suit.Also: "delayed surface marker buoy" and "decompression buoy"
An inflatable marker buoy deployed from underwater to indicate the position of a diver and to control ascent rate. Can also be used to mark a position or signal an emergency.Subsection: Top, Da, De, Di, Do, Du
Main article: Duckbill valve
A non-return valve, manufactured from rubber or synthetic elastomer, and shaped somewhat like the beak of a duck. Used as exhaust valve in some twin-hose diving regulatorsSee: Dynamic positioning
Vessel which maintains position and heading using thrusters and positional feedback [41]Main article: Dynamic positioning
Method of keeping a floating platform in position without anchoring, using thrusters and positional feedback.Also: "floating setpoint"
A target value for oxygen partial pressure in a rebreather loop which varies as a function of depth. Generally a setpoint that changes to optimize gas use, no stop time and other dive variables.[21]Main article: Dysbarism
Medical conditions resulting from changes in ambient pressure.Contents: Top |
Main article Ear clearing
Equalising the pressure in the middle and external ear by opening the Eustachian tubes. Several techniques are used.[46]See: Diving rebreather#Control of the breathing gas mix
Electronic closed circuit rebreather. Sometimes ECCCR for electronically controlled closed circuit rebreather, which is the same thing.See: Eddy-current testing
Method of non-destructive testing using electromagnetic induction to detect flaws in conductive materials. It is used to detect cracks in parallel neck threads of aluminium cylinders. Also called Visual Plus inspection. Required for cylinders of AA6351 alloy.See: emergency gas supply
See: VVAL18
Main article: electro-galvanic oxygen sensor
An Electro-chemical fuel cell which produces a voltage proportional to the partial pressure of oxygen.See also: bailout cylinder
Main article: Bailout bottle, also Surface-supplied diving#Bailout gas supply
Breathing gas supply to a diver that is intended for use in a failure of primary, and where applicable, secondary, breathing gas supply systems. More than one emergency gas supply may be available, of which at least one is usually carried by the diver (scuba).Also: "emergency beacon" or "EPIRB"
Main article: Emergency position-indicating radiobeacon station
Tracking transmitters which aid in the detection and location of boats and people in distress at sea.Also: "ESA", "Controlled emergency swimming ascent", "CESA"
Emergency procedure where the diver makes an ascent at approximately neutral buoyancy from depth after a breathing gas supply failure.See: nitrox
Also: "EAD"
Main article: Equivalent air depth
Depth at which partial pressure of nitrogen in a nitrox mixture at a given depth is equal to the partial pressure of nitrogen in air. Used for approximating the decompression requirements of nitrox mixtures by finding the depth at which air would require the same decompression. Based on exposure to equal partial pressures of nitrogen at maximum depth.[6]Also: "END"
Main article: Equivalent narcotic depth
A way of expressing the narcotic effect of a breathing gas mixture at depth by comparison with the depth at which air would have a similar effect. Used to choose nitrogen content of a Trimix breathing gas for a planned dive profile to limit nitrogen narcosis. Based on limiting the partial pressure of nitrogen during the dive by diluting the breathing gas with helium.Main article: European Diving Technology Committee
International committee of European representatives promoting good standards for diving and co-ordinating, where possible, differing standards with the aim of making European professional diving safer.[4][48]See: Saturation diving#Excursions from storage depth
In Saturation diving an excursion is a lockout dive in which the diver is exposed to a depth pressure significantly more or less than the saturation storage depth, usually within limits that allow excursion and return to the storage depth without decompression being required before, during, or after the excursion. It can also mean a significant stepwise reduction of pressure at the start of decompression from saturation to a depth pressure which will maximise the utility of the oxygen window of the breathing gas, to reduce the total duration of decompression. This is not allowed by some decompression schedules.[50]Also: "ventilation/oxygen extraction ratio"
Ratio between minute ventilation and oxygen uptake, the volume rate of gas breathed to the amount of oxygen taken up in the bloodstream. A typical surface extraction ratio of 20 would mean that for every 20 litres of gas breathed, 1 litre of oxygen would be absorbed in the lungs.Contents: Top |
Subsection: Top, Fa, Fe, Fi, Fo, Fu
Also: "FMEA"
See: Failure mode and effects analysis
A methodology used to identify potential failure modes, determine their effects and identify actions to mitigate the potential failures.[20]Also: "FMECA"
See: Failure mode, effects and criticality analysis
An extension to FMEA of a criticality analysis, which combines the probability of failure modes with the severity of their consequences to identify relative risk of each mode, allowing remedial effort to be directed where it is likely to produce the greatest effect.[20]Main article: Fatigue (material)
Cracking in a material resulting from multiple stress cycles below the ultimate or yield strength. Usually refers to large number of cycles.Subsection: Top, Fa, Fe, Fi, Fo, Fu
See: feet sea water
Unit of pressure equal to 1/33 atm. Not a linear measure of depth. Generally defined as the pressure exerted by a foot depth of seawater having a specific gravity of 1.027 and is approximately equal to 0.445 pounds per square inch.[20]See: full-face mask
See: Feet fresh water
Feet fresh water. Unit of pressure equal to 1/34 atm. Not a linear measure of depth.Subsection: Top, Fa, Fe, Fi, Fo, Fu
See: Diving air compressor#Filling diving cylinders and Diving cylinder#Filling
High pressure flexible hose used to connect a cylinder to the storage cylinder, filling panel, booster or compressor, through which high pressure gas flows to fill the cylinder.Main article: Filtration
Process for removing impurities from a fluid. Particulates are commonly removed by passing the fluid through porous material with pore size small enough to trap the particles (e.g. micron filters). Liquids and gases are commonly absorbed or adsorbed by the surface of the filter medium (e.g. activated carbon, molecular sieve, silica gel), or may be chemically combined with the medium (e.g. Sodalime) or catalytically converted (e.g. Hopcalite) into a less objectionable substance.Also: "fin holders", "fin fasteners", "fin grips", "fin keeps", "fin guards", "flipper fixers", "Y-straps", "ankle straps", "accessory safety straps", "fix fins", "grip fins" and, in recognition of their French origin, "fixe-palmes".
See: Swimfin#Attachment
Y-shaped elastic rubber straps worn over the arch, the heel and the instep of each foot to help prevent swim-fins from falling off the diver's feet. Mainly used with full-foot-pocket fins.See: dynamic setpoint
Also: bell flooding valve[53]
A valve in a diving bell which allows air to escape and internal water level to rise. This can be useful to assist the bellman in recovering an incapacitated diver through the bottom hatch.[54][55]Main: Fluoroelastomer
Synthetic elastomers (rubber) with good performance in high partial pressures of oxygen. Preferred material for o-rings in diving regulators for oxygen service.See: diluent flush
See: Finning techniques#Flutter kick
finning style where the fins are alternately moved up and down by movements of the full leg.[1] Thrust is developed on both up and down strokes. Vortices shed move both upwards and downwards. See also modified flutter kick.Subsection: Top, Fa, Fe, Fi, Fo, Fu
Main article: Anti-fog
Condensation of water vapour on the inside surface of a mask or helmet faceplate, reducing visibility.See: Scuba skills#Entries
Water entry technique used by scuba divers from a boat or platform too high or unsuitable for backward roll entry. The diver bends forward at the hips and waist and falls forward into the water, making a partial somersault and breaking the water with the cylinder, back and shoulders. Not suitable for heights more than about 2 m, and can be problematic if the diver is carrying several heavy items like stage cylinders or large cameras.See also: free gas
Air at normal atmospheric pressure.Main article: Free-diving
Underwater diving that does not involve the use of external breathing apparatus, but relies on a diver's ability to hold their breath until resurfacing. See also breath-hold diving, and apnea (q.v.)Main article: Ear clearing
Technique for equalising the middle ear by pinching the nose closed and moving the back of the tongue upwards.Main article: Frog kick
Finning technique where thrust is developed by sweeping the fins horizontally toward each other with the fins twisted into a nearly vertical plane, with the soles facing each other, followed by a recovery stroke which develops negligible thrust where the fin blades are feathered. The legs are fairly straight during the power stroke. See also: modified frog kick.Main article: Frogman
A scuba diver, particularly a military diver on an undercover mission.See: feet sea water
Subsection: Top, Fa, Fe, Fi, Fo, Fu
See: Duplex (telecommunications)#Full duplex
Voice communication system where both users can transmit and receive at the same time. Compare with half duplexContents: Top |
Subsection: Top, Ga, Ge, Gi, Go, Gu
See also: jump
The space between two cave guidelines. Usually between a main guideline and the start tie-off of a branch line.See: Distance line#Spools
A relatively short length of cave line on a spool used to bridge a gap between lines when making an excursion from the main guideline to a branch guideline. The line is left in place during the excursion, and usually retrieved on the way outAlso: "gator" (US)
Textile legging wrapped around the calf and ankle area over a dry suit to restrict the amount of air that can get into the lower leg area. Also can reduce drag of the suit in this area by smoothing over creases and folds.Main article: Gas blending for scuba diving
Mixing breathing gases for diving, filling diving cylinders with gas mixes such as nitrox or trimix.See: gas switching block
Main article: Gas embolism
Blockage of a blood vessel by a bubble of gas.Main article: Gas composition
The fraction by molecular count, volume or pressure (they all come to the same thing) of a specific gas in a mixture of gases.See: Scuba gas planning#Gas matching
The calculation of reserve and turn pressures for divers using different cylinder volumes on the same dive, allowing each diver to ensure that sufficient gas is retained at all times to allow for foreseeable contingencies based on each diver's cylinder volumes, and both divers' individual gas consumption rates.[59]See: inert gas narcosis
See: Gas switching
The procedure of changing from one breathing gas mixture to another during a dive. This may be done to avoid oxygen toxicity, hypoxia, or nitrogen narcosis, to accelerate decompression, or to avoid running out of breathing gas. Generally applied to open circuit breathing equipment, where a physical change-over of gas source is made. In closed circuit systems the gas composition is continuously controlled to follow the chosen set-point.See: Dive computer#Additional functionality and features, Dive computer#Management of violations
Operating mode for a personal dive computer where the decompression calculation is disabled, and the unit operated only as a timer and depth gauge. Typically used when diving with gas mixtures not supported by the algorithm, in which case decompression tables are used to monitor and control the decompression schedule. Some dive computers will automatically switch to gauge mode if the diver violates a depth limit, leaving the diver without decompression information.Main article: Pressure measurement#Absolute, gauge and differential pressures - zero reference
Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressureMain article: Gay-Lussac's law
Relation between temperature and pressure in an ideal gas for a constant volume.Subsection: Top, Ga, Ge, Gi, Go, Gu
See: stride entry
Also: "buccal pumping", "lung packing"
A method used by freedivers for filling the lungs with more air than maximal inspiration to normal total lung capacity (TLC). After a full inhalation, the diver fills the mouth with air, while the glottis remains closed, then opens the glottis and forces this air into the lung using the cheeks and tongue to reduce the mouth volume. This may be repeated several times.[60]Subsection: Top, Ga, Ge, Gi, Go, Gu
Main article: Global Positioning System
A satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellitesSee: Decompression theory#Gradient factors
A way of modifying the M-values of a decompression algorithm to more conservative values in proportion to depth. Often used to bias the algorithm towards deeper stops by using a smaller value for the deeper value.See: distance line
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