See the Outline of underwater diving for a hierararchical listing of underwater diving related articles grouped by topical relevance
Surface-supplied divers riding a stage to the underwater workplace
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:
Aluminium alloy 6351 is subject to sustained load cracking and requires periodical eddy current testing to identify crack development at an early stage.[1] Not used for new cylinder manufacture since 1988, but many cylinders of this alloy are still in service.[2]
System for semi-closed circuit rebreather feed gas addition in which gas is added to the breathing circuit by a mechanism, regardless of current volume, and excess gas is vented to keep the loop volume within limits. Compare with passive addition
active heave compensation
Automated system using inertial feedback to adjust lifting cable length to compensate for the movement of the lifting point, to minimise vertical movement of the load.[4]
Part of a launch and recovery system. A gantry crane, sheer-legs or davit structure for launching and recovering diving bells, diving stages, anchors, or large ROVs.[6][7] Usually deployed by hydraulic rams which luff the frame over the deck or overboard as required. The load is hoisted and lowered by cables from the top of the frame.
Decompression schedule tending to shorter overall decompression time for a given pre-ascent dive profile, accepting increased risk of decompression sickness to reduce the overall ascent time.[8]
Feature of some dive computers to measure cylinder pressure using an integral pressure gauge connected by HP hose to the regulator first stage, or receive data from one or more remote pressure transducers fitted to the HP port of a regulator, and display the pressure on the screen. Other features may also be available using the data.[10]
A device based on a steeply rising pipe, used by divers to suck small objects, sand and mud from the sea bed and to transport the resulting debris upwards and away from its source. Air is injected into the lower end of the pipe and the rising bubbles entrain water and cause an upward flow which draws the material from the bottom along.[11]
Surface-supplied diving where the breathing air is supplied to the diver by a simple hose. The diver usually breathes through a mouth held demand valve.
A rapid increase or accumulation in the population of algae (typically microscopic) in an aquatic system. Some blooms may be recognized by discoloration of the water resulting from the high density of pigmented cells. Visibility can severely deteriorate over a period of hours to days.[13]
Diving at a location where the water surface is at an altitude which requires modification of decompression schedules.[20] (more than about 300 m (980 ft) above sea level.
A breathing gas mixture that is suitable in composition and temperature, and of adequate pressure, having regard to the system and equipment used in the diving operations, the work undertaken in those operations, and the conditions and depth at which they are to be carried out.[25]
Decompression model in which the filtering capacity of the lung is assumed to have a threshold radius of the size of a red blood cell and sufficiently small decompression bubbles can pass to the arterial side, especially during the initial phase of ascent.[27]
A waistcoat (vest) style harness of heavy cloth with strong adjustable webbing straps so that the diver can not slide out under any reasonably foreseeable circumstance.[29]
Part of the dive profile where the diver is moving upwards towards the surface. An ascent may be interrupted by stops (q.v.), when the diver maintains a functionally constant depth for the purpose of decompression, and pulls (q.v.), during which periods there is consistently upwards movement (minor variations in the scale of a few seconds are generally ignored).
A small one-man articulated submersible of anthropomorphic form which resembles a suit of armour, with elaborate pressure joints to allow articulation while maintaining an internal pressure of one atmosphere.[31]
A mechanism for automatically closing off the inlet opening of a regulator first stage when it is disconnected from a cylinder to seal it against ingress of contamination.[32][33]
A demand valve set into the breathing loop of a rebreather to inject diluent gas into the loop when the loop volume falls and there is not enough gas for inhalation.
automatic dump valve
Adjustable spring-loaded overpressure valve with manual override used on a constant volume dry suit to automatically discharge excess suit inflation gas as it expands during ascent, thereby maintaining a nearly constant volume and buoyancy of the suit.
EN 14153-2 / ISO 24801-2 standard competence for recreational scuba diver. The level 2 "Autonomous diver" has sufficient knowledge, skill and experience to make dives, in open water, which do not require in-water decompression stops, to a recommended maximum depth of 20 m with other scuba divers of the same level, only when appropriate support is available at the surface, and under conditions that are equal or better than the conditions in which they were trained, without supervision of a scuba instructor, unless they have additional training or are accompanied by a dive leader.[34]
Breathing gas available from a cylinder after taking into account ambient pressure and the pressure needed for correct function of the delivery system at a useful flow rate. This may also take into account a reserve allocation.
A finning technique for moving backwards. Not an easy, powerful or elegant kick, but useful in many situations. The fins are angled outwards in opposite directions with the legs straight, then swept upwards and towards the diver by bending the knees in the power stroke. The knees may move downwards a bit at the same time by bending at the hips for stability. The return stroke feathers the fins by pointing them backwards in line with the body axis, to reduce forward thrust until the legs are straight again
backmount
back mount
The practice of carrying a scuba set on the back of the diver, supported by a harness, backplate or stabilisor jacket BCD. Compare with sidemount
backpack
A rigid or semi-rigid structure similar in function to a backplate, usually made of moulded plastic, but sometimes of metal, used either as a stiffener and reinforcement for a jacket style buoyancy compensator, or as the basis of a scuba harness independent of a buoyancy compensator. The backpack supports and stabilises the scuba cylinder on the diver's back.
A plate, normally made from metal, which rests against the diver’s back, and to which the primary scuba cylinders are attached. Held to the body by harness straps over the shoulders and round the waist. Sometimes also crotch straps and chest straps. Usually used with a back inflation buoyancy compensator.
Water entry method in which the seated diver rolls backwards off the side of the boat, allowing the scuba cylinders to strike the water first.[36]: 125
bailout block
A gas switching block specifically intended for connection of a bailout set to the main gas supply (which may be scuba or surface supply) which allows the diver to switch from main gas supply to emergency gas supply while continuously using the same mouthpiece, regulator second stage, full face mask or helmet. A bailout block is generally used on open circuit breathing apparatus, the equivalent function on a rebreather is provided by a bailout valve (BOV). The bailout block may be mounted on the side of a diving helmet or full-face mask, or may be mounted in a convenient place on the diver's harness, and includes a bailout valve, used to select the gas source, and one or more non-return valves to ensure that the emergency gas supply is directed only to the diver.
An independent breathing gas supply carried by a diver for use in case of failure of the main gas supply. Usually consists of a bailout cylinder with a first stage regulator, and either a second stage regulator or connected to a bailout block or bailout valve (q.v.) A submersible pressure gauge is also usually provided.[37]
bailout valve
1. Also: "integrated open-circuit regulator"An open circuit demand valve built into a rebreather mouthpiece, or other part of the breathing loop, which can be isolated while the diver is using the rebreather to recycle breathing gas, and opened at the same time as isolating the breathing loop when the diver bails out to open circuit.[38]
2. A valve which opens the gas supply from the bailout cylinder of a surface supplied diver, used in case of surface gas failure, usually mounted on the side of a diving helmet or full-face mask, or on a manifold block on the diver's harness.
A heavy duty full-face mask with many of the characteristics of a lightweight demand helmet. In structure it is the front section of a lightweight helmet from above the faceplate to below the demand valve and exhaust ports, including the bailout block and communications connections on the sides. This rigid frame is attached to a neoprene hood by a metal clamping band, hence the name.
1. Also: "tank factor". Numeric value computed for a cylinder or manifolded set that relates volume and pressure in the imperial system of units. Computed by dividing nominal capacity (cubic feet) by cylinder working pressure (psi) to express cubic feet of volume per psi of fill pressure (sometimes multiplied by 100 to give cubic feet per 100 psi). Used to convert cylinder pressure to free gas volume.[9]
2. A line that is a base for measurement or for construction; see datum (calculations or comparisons)
3. A data set which is a point of reference (engineering or science) for later data.
Uncontrolled buoyant ascent caused by inability to release gas from the buoyancy compensator faster than it expands due to pressure reduction of ascent.
A person on the beach who records when divers enter and exit the water. Typically used during recreational scuba training to keep track of the students, watch the gear, and provide assistance when required.
Surface oriented diving operation in which the divers are transported in and deployed from a closed bell, and are either decompressed in the bell at the surface or transferred under pressure to a deck decompression chamber for decompression.
Mechanism or structure for guiding and constraining the motion of a bell when in the close vicinity of the deployment platform to improve handling in bad weather.[6]
bell diving
1. Any diving operation in which the divers travel in or work from a diving bell
2. Diving operations in which divers are transported in and deployed from a closed bell, either as a surface oriented (bell bounce) or saturation dive.[37]
bell harness
A safety harness made of strong webbing, which is fastened around a diver over the exposure suit, and allows the diver to be lifted without risk of falling out of the harness.[40]
The part of a bell dive operation from bell lock-off to bell lock-on (from and back to the life support system)[6]
bell stage
A framework extending below a closed bell which keeps the base of the pressure vessel off the bottom sufficiently to provide clearance for the divers to use the bottom hatch when the bell is resting on the bottom or on the clump weight.
The combined supply and return hoses and cables for life-support, power and communications between a diving bell and the support platform
belt slide
belt slider
Also: "triglide", "weight slider", "weight stop"
Hardware item with two parallel slots which is fitted to harness or weightbelt webbing to prevent other components such as D-rings and weights from sliding along the webbing.[9]
Sometimes also referred to as confined water. Environments of low risk, where it is extremely unlikely or impossible for the diver to get lost or entrapped, or be exposed to hazards other than the basic underwater environment.
bent D-ring
A D-ring which has been bent about 45° near the straight section on both sides, forcing it to project slightly from the harness when pushed to one side, allowing easier attachment of clips.
bends
Decompression sickness: Injury caused by bubble formation in the body tissues after hyperbaric exposure.
Three D-rings welded together along their straight sides so that one is perpendicular to the other two, which lie on the same plane. This uses the two flat rings to maintain the third in an upright position when mounted on harness webbing, allowing it to be more easily accessed to clip on stage cylinders. Named after Billy Deans.[9]
A type of safety lifting hook which is held closed when under load by a lever system where the weight of the load holds the bill of the hook against the safety latch.[44]
Mixing tube in which gases are continuously mixed prior to intake by a compressor, usually at atmospheric pressure.[12] Usually refers to manufacture of nitrox from air with added oxygen, but also used for trimix. Gas mixture is usually continuously analysed at the exit of the blending stick to monitor composition.
blind traverse
Passing through a cave from one entrance to a different exit which the diver has not used before.[9]
block adaptor
Screw-in adaptor fitting which is fitted to a 200/240 bar DIN pillar valve to allow connection of a yoke regulator or filling whip.
blowdown
1. Procedure of pressurising a diving chamber or saturation habitat.
2. Procedure of driving water out of the bottom of an open diving bell by displacing it with air or other breathing gas at ambient pressure.
A sink hole in a lake or the sea that is often the entrance to a cave. Blue holes in the sea are subject to tides so that their flows regularly reverse.[9]
A metal connector comprising a hook with a spring-loaded axial sliding rod gate which must be manually retracted to allow the hook to be clipped onto something or removed. May be single- or double-ended, and if single-ended is usually fitted with a swivel ring opposite the jaws.
bomb
Commercial diver slang for high pressure gas storage cylinder of around 50 litres water capacity, also known as a "J".
bommie
Australian term for a coral mound or small, usually isolated reef, or coral head. From the Aboriginal word "bombara".
Time used in calculating decompression obligation from decompression tables. For most tables this is defined as the elapsed time from starting the descent to starting the final ascent to the surface, excluding ascent and decompression time.[47]
bottom timer
Device used to measure and record the total time spent underwater during a dive. They do not generally only record bottom time (q.v.).
bottom out
A rebreather counterlung becoming completely deflated during inhalation.[48]
bounce dive
bounce diving
1. Also: "surface oriented dive" : In commercial diving, bounce diving is the alternative to saturation diving. Any dive where the diver is decompressed directly after the dive.[25]
2. In recreational diving, a bounce dive is a descent to maximum depth and then a direct ascent back to the surface with minimal bottom time, in a dive profile resembling a spike.
Relationship between pressure and volume at constant temperature in an ideal gas.
breakdown room
An area in a cave where a large amount of material has fallen from the overhead.[9]
breakout
The point at which an object being lifted which is partly embedded in the bottom sediments overcomes the adhesion of the sediments and the force required to lift it drops rapidly to the apparent weight of the object.
breakthrough
The failure of a rebreather scrubber to remove all the carbon dioxide in the gas passing through the absorbent material.[48]
Gas supplied to the diver to breathe, either directly to the diver or to the hyperbaric environment of the diving bell, dive chamber or saturation habitat.[37][47] Colloquially just "gas" or "mix".
breathing hose
Large bore hose carrying the breathing gas in a rebreather breathing loop[48] or a twin-hose demand valve.
breathing loop
The gas flow path in a rebreather comprising the diver's lungs, the mouthpiece, valves, hoses, counterlungs and scrubber through which gas is rebreathed.
B-ring
A small plate with a slot for a webbing belt and two side by side holes for clipping on equipment, generally used similarly to a D-ring in combination with a belt slider as an alternative to a butterfly slider
Broco cutter
A type of thermal lance initiated by an electric arc, in common use for underwater cutting work.
A procedure carried out by scuba divers using the buddy system where each diver checks that the other's diving equipment is configured, fitted, and functioning correctly just before entering the water to dive.
A short line between two divers, used to maintain contact during a dive, generally in poor visibility, or other conditions where the divers might become separated and not be able to quickly locate each other.[47]
Diving tables and decompression algorithm on which the tables are based, and some dive computers are programmed, based on the dissolved gas decompression model derived and tested by Dr Albert A. Bühlmann.
built in breathing system
Also: "BIBS"
A demand breathing gas supply system with external exhaust used to provide chamber occupants with breathing gases other than the gas used to pressurise the chamber. Used for treatment gases and emergency breathing gas if the chamber is contaminated.[20]
bundle
A set of gas cylinders fastened together for transportation and manifolded for use as a unit,[49] also cylinder bundle.
Length of shock cord used to restrain the top end of side mount cylinders and keep them tucked in at the diver's shoulder while swimming.[39] Usually clipped to a shoulder D-ring of the harness and looped around the cylinder valve. May be attached to the back of the harness between the shoulder blades, or run continuous from one shoulder D-ring, around the back under the arms to the other shoulder D-ring.
bungee wing
Back inflation buoyancy compensator with shock cord lacing or loops which exert a force on the bladder to oppose expansion during inflation and accelerate deflation.
1. Upward force on an object immersed in a fluid due to pressure exerted over the immersed surface.
2. Resultant upward force of buoyancy and weight of an object immersed in a fluid.
buoyancy check
Procedure to test and adjust weights carried by an underwater diver. The diver wears all the personal equipment to be used for the planned dive, with the scuba tank(s) nearly empty, and the buoyancy compensator empty, in shallow water of the same density as expected on the dive, and adds or removes weights until neutrally buoyant. After the buoyancy check it is usual to distribute the weights for safety, trim and convenience.
An airtight bladder worn by a diver which can be filled with air and vented to adjust and control the buoyancy of the diver.
buoyancy control
The skill of maintaining the appropriate buoyancy at any time during a dive.
burn tester
Device for measuring the actual capacity of a battery relative to its nominal capacity, and the associated functional time for the device that the battery is powering.[9]
burn time
The effective use time of a battery powered device. Mainly used in reference to dive lights and scooters.[9]
A non-reclosing pressure relief device used to protect a diving cylinder from overpressurization.
butterfly clip
A type of bolt snap with a tapered guide gate opening formed by a protrusion on both the piston and the fixed sides of the gate.[9]
butterfly slider
butterfly D-ring
A plate with two D-shaped cutouts on opposite sides of two to four parallel longitudinal slots for webbing. Used at the top back of the crotch strap in place of a butt-plate (q.v.) on minimalist sidemount harnesses as a clip-on point for equipment.[39]
butt-plate
A rigid or fairly stiff flexible lower extension to a backplate or other scuba harness supporting butt-plate rails, used for clipping off the lower end of sidemount cylinders to the harness.[39]
A strap, usually of webbing, with a cam action tensioning buckle, generally used to secure a diving cylinder to a backplate, stabilisor jacket BCD or other form of diving harness.
The toxic effects of carbon dioxide, due to incomplete elimination of carbon dioxide resulting from skip breathing, excessive work of breathing, scrubber failure in a rebreather system, or inadequate ventilation in a diving chamber or free flow helmet. Occasionally caused by contaminated gas supply.
An emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest
Decanting from several storage cylinders in succession, generally using a procedure to maximise charge pressures. Often used in partial pressure gas blending.
catenary anchor leg mooring
Also: CALM
Single point mooring type named for the catenary curve of the anchor cables that hold the buoy in position. Also referred to as single buoy mooring, monobuoy or loading buoy.[6]
A mixture of water and carbon dioxide absorbent caused by flooding the scrubber of a diving rebreather, and which may reach the diver's mouth through the breathing loop. The alkalinity depends on the absorbent used, and may injure the diver if aspirated.
A naturally occurring cavity in bedrock, or an underwater passage not illuminated by natural daylight, large enough to be entered by a human. Statute 810.13 of the Florida legislature defines a cave as: any void, cavity, recess, or system of interconnecting passages which naturally occurs beneath the surface of the earth or within a cliff or ledge, including natural subsurface water and drainage systems but not including any mine, tunnel, aqueduct, or other manmade excavation, and which is large enough to permit a person to enter. The word "cave" includes any cavern, natural pit, or sinkhole which is an extension of an entrance to a cave.[9]
Directional line markers which point the way to an exit.
cave fill
Filling a scuba cylinder to a pressure significantly above the rated safe working pressure (charging pressure).[9] Illegal in some jurisdictions, and increases risk of catastrophic failure.
cave line
1. Application: A distance line laid in a cave for navigation.
2. Material: Small diameter braided synthetic cordage used for distance lines in cave diving .
A reel specifically made for cave diving, used to lay and recover large lengths of cave line which is used as a temporary guide line to find the exit or a permanent guide line.
cavern
1. Two or more interconnected underground rooms or passages in bedrock, each large enough to be entered by a human.[9]
2. The initial space in an underwater cave system that is illuminated by natural daylight.[9]
3. A naturally occurring cavity in bedrock or an underwater passage, large enough to be entered by a human, which is illuminated by natural daylight, or in which it is possible from all points to see the exit by natural daylight.[9]
cavern dive
Defined as a penetration dive under rock where visibility is greater than 40 feet, maximum penetration does not exceed 130 feet, maximum depth does not exceed 70 feet, the diver is always within the area illuminated by ambient sunlight, and does not pass through any restrictions.[9]
A sinkhole in Mexico. Generally with vertical or overhanging walls or shafts with water that open into a cave system.[9]
certification card
A plastic card issued to a diver by a diver certification agency as evidence of having completed the diver training and experience required for the level of certification.
Ring or hook shaped components used for installing and recovering conventional mooring systems. The chaser is hooked around the chain and pulled in the direction of the anchor until it slides onto the anchor shank and is stopped by the crown. The chaser is then used to break the anchor out by pulling directly upwards.[6]
chamber dive
Simulated dive in a hyperbaric chamber pressurised to equivalent pressure to the nominal depth of the dive.[47]
Formation of void spaces in the granular absorbent in a scrubber which allow gas to bypass close contact with the absorbent material, allowing carbon dioxide to pass through the scrubber.[48]
Pressure stamped on a container for a permanent gas to indicate the maximum gauge pressure measured at, or corrected to the reference temperature (usually 15°C or 20°C) that may be applied at the time of filling.[51]
A dive done to establish whether a diver's skills are current and responses appropriate and timely, equipment is configured and working correctly, or that team procedures are mutually understood and work as planned.
chicken vest
Sleeveless neoprene wetsuit vest with attached hood.[52][53]
chimney
A section of a cave that is vertical or near vertical and like a shaft.[9]
Chinese lantern
Connection between pipeline end manifold (PLEM) and single point mooring buoy (SPM) using two to four separate curved, flexible, underwater hose strings.[6]
A strap around the neck of a sidemount cylinder used to hold the bolt snap closer to the neck so that the head of the cylinder stays closer to the diver's armpit. The choker can be a small webbing strap with a sliding buckle for adjustment, so it can be tightened to bring the clip closer to the neck or slacked off while in use.
A symptom of decompression sickness manifested by shortness of breath, caused by a large number of venous gas bubbles in the lung capillaries which interfere with gas exchange.[46]
An assembly of valves, spools, and fittings installed on top of the wellhead and used primarily to control the flow, usually oil or gas, out of the well.[6]
Christmas tree ladder
A boarding ladder which has a single central rail with rigid cantilevered rungs to each side, allowing use while wearing swimfins.[54]
A closed or dry bell is a pressure vessel for human occupancy which is lowered into the sea to the workplace, equalised in pressure to the environment, and opened to allow the divers in and out. Divers may be decompressed in the bell or transferred under pressure to a hyperbaric chamber at the surface.
Underwater breathing apparatus in which exhaled gas is scrubbed to remove carbon dioxide, and the oxygen is replenished to maintain a specific partial pressure, before returning it to the diver as breathing gas. See alsoECCR and MCCR.
A weight used to keep the guide wires of a diving bell aligned and tensioned.
clusterfuck
Also: "CF", "charlie foxtrot"
Occasion when the situation diverges notably and usually uncontrollably from the plan, sometimes involving immediate hazard to life and limb, and often involving poor judgement.[46]
A systematic set of professional standards or written guidelines and rules of procedures to be followed by members of a profession, trade, occupation or organization. A code of practice may be compiled and agreed on by members of a particular profession or written guidelines issued by an official body or a professional association to its members to help them comply with its ethical standards. A code of practice does not normally have the force of law, but is often required or compulsory practice for members of an organisation.
coded welder
Welder who is trained and qualified and assessed as competent for a specified type of welding under specified conditions.
Person trained in scuba diving or swimming underwater in a military capacity which can include combat
command signal
A signal from a diver in a team that requires a response from the other diver. There are three: "Are you OK", "Hold", and "Surface" (terminate the dive).[9]
The process of making a well, that has been drilled, ready for production.
competent person
Person who is able to perform a task or operation safely and according to required procedures. Recognition of competence may require formal assessment or accreditation, or registration with government body.[51]
An American trade association for the industrial and medical gas supply industries.[55] The CGA publishes standards and practices that codify industry practices. In cases where government regulation is not specific, CGA documents are considered authoritative. CGA V-1 Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections covers diving cylinder valve outlets.[56] Safety devices like burst disk overpressure protection are specified by the CGA Standard S1.1.
compressed neoprene
Foam neoprene that has been compressed to reduce volume. Used for dry suits and hot water suits which are less affected by depth induced buoyancy changes.
compression
The process of increasing the ambient pressure on a diver by descending into the water or pressurising the chamber.[37]
Machine which pressurises gas. Generally intake gas is at ambient pressure, outlet gas at higher pressure. High pressure breathing air compressor output pressure is usually 200 to 330 bar. Machines which compress gas at higher intake pressures are called boosters
compressor log
Book or file containing records of compressor operation, filling of cylinders and maintenance records.
compressor operator
Person who operates a compressor, either to fill cylinders, or to provide breathing air to surface supplied divers.
Water that is enclosed and bounded sufficiently for safe training purposes. Generally implies that conditions are not affected by geographic or weather conditions, and that divers cannot get lost.[57]
Decompression profile tending to minimise risk of decompression sickness at the cost of more decompression time for a given pre-ascent dive profile.[8]
constant depth blackout
constant pressure blackout
Also: "isobaric blackout"
A Freediving blackout which occurs while the diver maintains a near constant shallow depth, where reduction of oxygen partial pressure due to ascent is not a factor. Usually induced by pre-dive hyperventilation. Also referred to as shallow water blackout, which is an ambiguous term
Decompression without stops. Instead of a fairly rapid ascent rate to the first stop, followed by a period at static depth during the stop, the ascent is slower, but without officially stopping. Ascent rate may vary with depth, usually slowing as the depth reduces.
contra-indications to diving
Conditions (usually medical) that indicate that a person should not dive.
control compartment
The tissue compartment that dictates the ascent profile of a given dive because it is theoretically the highest risk compartment for DCS.[8]
An emergency technique for surfacing, usually when no breathable gas is available at depth. The diver fins upward while gently exhaling to keep expanding air in the lungs from causing lung expansion injuries.[58]
A diving helmet of traditional design and construction, usually made from spun or beaten copper, with brass or bronze fittings. There are usually two main sub-assemblies; the bonnet is the roughly spherical part which covers the head and is provided with viewports, valves and various other fittings, and the corselet, which rests on the upper torso of the diver, and to which the bonnet is connected when in use, and which may be sealed to the suit and ballasted to compensate for the buoyancy of the airspace inside the helmet.
Lower part of a standard copper helmet and some other heavy helmets, which clamps to the diving suit, rests on the diver's shoulders, and to which the helmet upper part, or bonnet, is clamped, screwed or bolted.
Pressure required to open a spring-loaded valve. Often applied to the difference in pressure over the diaphragm of a demand valve required to open the valve to start flow. This may differ significantly from the pressure difference required to keep the valve open once flow has been initiated, and the pressure required to keep the valve open may vary with flow rate.
The amount of breathing air required to safely exit a penetration dive. When the available air supply reaches the calculated critical pressure the dive has reached a planned turning point.[9]
Hypothesis that bubble formation during decompression will not occur if a critical pressure difference between tissue inert gas tension and ambient pressure is not exceeded.
critical flicker-fusion frequency
Also: CFFF
The frequency at which a flickering light is perceived as continuous, a measurement used to evaluate visual temporal processing as an indicator of alertness and arousal in humans, including use as an experimental indicator of inert gas narcosis in divers, using a simple uncomplicated, non-invasive and objective methodology.[59]
Hypothesis that bubble formation during decompression will not occur if a critical ratio of tissue inert gas tension and ambient pressure is not exceeded.
Hypothesis that symptoms of decompression sickness will not be evident if a critical volume of tissue gas bubbles is not exceeded.
cross hauling
cross-hauling
Exerting a lateral force on the bell by using a separate cable from a winch. Used to prevent bell rotation on the lifting cable if a clump weight with guidelines is not used, to move the bell to a position other than directly below the launch and recovery system, and may be used to recover a bell in an emergency.[60]
crotch strap
Harness strap that passes from the lower part of the harness at the back, through between the diver's legs, to the waistbelt in front of the harness, effectively securing the harness from sliding up along the torso. In commercial diving safety harness this is often in two parallel parts and allows the diver to be lifted by the harness without risk of falling out.[9]
crushed neoprene
Proprietary material for dry suits manufactured by DUI in a process where the foam neoprene suit material is degassed by exposure to high hydrostatic pressure to reduce the volume after assembly. There is less buoyancy variation with depth as the material is less compressible after the treatment.[61]
A spring loaded over-pressure dump valve mounted on a dry suit sleeve near the cuff, usually relatively small and non-adjustable, which dumps excess gas from the suit if it is raised sufficiently.
cummerbund
A wide flexible rubber waistband, which helps to maintain a watertight seal between the jacket and the pants of a two-piece dry suit.
Common failure mode of an oxygen sensor cell in which an increase of oxygen partial pressure above the limiting level does not produce an increase in output current. Such a failure would prevent the control system from recognising an excessive partial pressure of oxygen.[48]
current shear
Variation in flow velocity along an axis othogonal to the direction of flow. Current shear may be vertical, where shallow water flows at a different velocity to deeper water, horizontal, where flow velocity varies across the width of the current, or mixed. Wind induced current displays vertical shear and directional variation with depth in an Ekman spiral.
The appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen.
cylinder
1. Diving cylinder: Refillable compressed gas container of water capacity between 0,5 L and 150 L used to supply gas for underwater diving.[51]
2. That part of a reciprocating compressor or booster in which the piston is moved to compress the gas. The internal space is cylindrical with a circular section. The external surface is usually finned for air cooling.
Rubber or plastic cover for the base of a scuba cylinder to protect it from abrasion, and in the case of domed end cylinders, to allow it to stand upright.
^British Sub-Aqua Club members (1982). British Sub-Aqua Club Diving Manual (10th ed.). Ellesmere Port, Cheshire: British Sub-Aqua Club. p. 199. ISBN978-0950678610.
^ abcdefghBevan, John, ed. (2005), The Professional Diver's Handbook, Submex
^Gibson, Victor (May 2009). "Glossary of terms". www.shipsandoil.com. Ships and Oil. Archived from the original on 9 January 2017. Retrieved 7 October 2016.
^ abc"Terms list"(PDF). Suunto Fused RGBM. Suunto Oy. 2012. Retrieved 4 May 2016.
^Busuttili, Mike; Davies, Trevor; Edmead, Peter; et al. (1959). Sport Diving. BSAC. pp. 72, 130. ISBN0-09-186429-1.
^Egstrom, G.H. (1992). "Emergency air sharing". Journal of the South Pacific Underwater Medicine Society.
^Wicks, R.E. (January 1989). "Alternobaric vertigo: an aeromedical review". Aviat Space Environ Med. 60 (1): 67–72. PMID2647073.
^Tjernström, O. (December 1974). "Function of the eustachian tubes in divers with a history of alternobaric vertigo". Undersea Biomed Res. 1 (4): 343–51. PMID4469100.
^Lundgren, C.E.G.; Tjernström, O.; Ornhagen, H. (September 1974). "Alternobaric vertigo and hearing disturbances in connection with diving: an epidemiologic study". Undersea Biomed Res. 1 (3): 251–8. PMID4469094.
^Staff (2008). "Abbreviations and definitions"(PDF). Diving Recommended Practice. Report 411. London and Brussels: International Association of Oil & Gas Producers. pp. 42–43. Archived from the original(PDF) on 28 October 2016. Retrieved 7 October 2016.
^After Cousteau himself, who had coined the word, the spelling was originally Aqua-Lung. See Jacques-Yves Cousteau & Frédéric Dumas, Le Monde du silence, Éditions de Paris, Paris, 1953, Dépôt légal 1er Trimestre 1954 - Édition N° 228 – Impression N° 741 (in French)
^Busuttili, Mike; Holbrook, Mike; Ridley, Gordon; Todd, Mike, eds. (1985). Sport diving – The British Sub-Aqua Club Diving Manual. London: Stanley Paul & Co Ltd. ISBN978-0-09-163831-3.
^ abcdStaff, EDTC (16 June 2017). "7 Definitions". Inshore and Offshore Diving Industry Personnel Competence Standards (Draft) (Report). European Diving Technology Committee.
^Haddock, Stephen H. D.; Heine, John N. (2005). Scientific Blue-Water Diving(PDF). California Sea Grant College Program. Archived from the original(PDF) on 25 March 2016. Retrieved 23 November 2018.
^ abcdDepartment of Labour (11 January 2002). Diving regulations 2001. Government Gazette, Republic of South Africa, Regulation Gazette No. 7243. Vol. 438. Pretoria: Government Printer. {{cite book}}: |work= ignored (help)
^SANS 10019:2019 South African National Standard: Transportable pressure receptacles for compressed, dissolved and liquefied gases — Basic design, manufacture, use and maintenance (8th ed.). Pretoria: South African Bureau of Standards. 2019. ISBN978-0-626-37092-3.
^ abcSouth African National Standard SANS 10019:2008 Transportable containers for compressed, dissolved and liquefied gases - Basic design, manufacture, use and maintenance (6th ed.). Pretoria, South Africa: Standards South Africa. 2008. ISBN978-0-626-19228-0.
^Rocco, Monica; Pelaia, P.; Di Benedetto, P.; Conte, G.; Maggi, L.; Fiorelli, S.; Mercieri, M.; Balestra, C.; De Blasi, R.A. (January 2019). "Inert gas narcosis in scuba diving, different gases different reactions". European Journal of Applied Physiology. 119 (1): 247–255. doi:10.1007/s00421-018-4020-y. PMID30350155. S2CID53040664.
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