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:
Subsection: Top, Pa, Pe, Pi, Po, Pu
Main article: Panic
A sudden sensation of fear which is so strong as to dominate or prevent reason and logical thinking, replacing it with overwhelming feelings of anxiety and frantic agitation consistent with an irrational fight-or-flight reactionSee: Decompression theory#Perfusion limited tissues and parallel tissue models
A decompression model comprising a group of tissues with varied rates of perfusion, but supplied by blood of approximately equivalent gas concentration. It is assumed that there is no gas transfer between tissue compartments by diffusion. This results in a parallel set of independent tissues, each with its own rate of ingassing and outgassing dependent on the rate of blood flowing through the tissueMain article: Partial pressure
(Abbreviation PP or pp) The pressure that a component gas of a gas mixture would exert if it alone was present in the volume occupied by the gas mixture.Also: concentration gradient
See: Molecular diffusion
The rate of change of partial pressure of dissolved gas through a solvent, which is the driving mechanism for diffusion through the solvent. Also loosely used to refer to the difference between the dissolved gas pressure in a tissue and ambient pressure.See: Rebreather#Passive addition semi-closed circuit
Feed gas addition system for semi-closed circuit rebreathers which discharges a part of the gas in the breathing circuit. fresh gas is added when the volume of the circuit decreases during inhalation and triggers the addition valve. Compare with active addition.See: patent foramen ovale
A common form of congenital heart defect that enables blood flow between the left and right atria through a gap in the interatrial septum. In some circumstances this may increase risk of decompression sickness if venous blood carrying gas bubbles is shunted into the arterial system, bypassing the pulmonary capillary network filter.Subsection: Top, Pa, Pe, Pi, Po, Pu
Also: "push-pull rebreather"
See: Diving rebreather#Breathing gas passage configuration
Rebreather with a single breathing hose from the mouthpiece to the scrubber and counterlung. Gas passes through it in both directions, unlike the one-way breathing loop configuration. The volume of the hose between the mouthpiece and scrubber is dead spaceSee: Penetration diving
Entering a region with no direct vertical access to the surface, such as a cave or the interior of a wreck.See: distance line
Main article: Perfusion
The passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue.See: Decompression theory#Deterministic models
The assumption in a decompression model that perfusion has the dominant influence on gas uptake and release. Compare with diffusion limited.See Diving cylinder#Permanent stamp markings
Text and symbols stamped into the metal of the shoulder of a diving cylinder providing obligatory and optional information about the cylinder.Also: "PLB"
Main article: Emergency locator beacon
Radio beacons for personal use which are intended to indicate a person in distress who is away from normal emergency services.Main article: Personal protective equipment
Equipment worn by personnel to reduce risk of injury at sites where it is not practicable to eliminate the hazard, including ear protectors, safety glasses, hard hats, gloves, overalls, respirators etc. Diving suits and underwater breathing apparatus are also personal protective equipment.See: patent foramen ovale
See: jump camera
A photograph of a quadrat taken for later analysis. Common in marine ecological research where in situ counting would be impractical. Quadrats may be identified by rigid frames or by a fixed camera to subject distance.Subsection: Top, Pa, Pe, Pi, Po, Pu
See: Pigging#Pipeline Inspection Gauge
Pipeline inspection gauge: A tool that is sent through a pipeline and propelled by the pressure of the product in the pipeline itself, for purposes such as cleaning, dewatering, inspecting, measuring, separation of contents, etc.See cylinder valve
Main article: Pin Index Safety System
Standard connection type for portable medical oxygen cylinder valves and regulators.Also: "PLEM"
See: Pipeline end manifold
The place where a flexible underwater hose string is attached to connect a seabed pipeline with a single point mooring.See: bolt snap
See personal locator beacon
See: pipeline end manifold
See: Surface-supplied diving skills#Breathing from a pneumofathometer hose
Use of the pneumofathometer hose to supply breathing gas to a surface supplied diver in an emergency. Supply can be from the diver's own pneumo hose or from a standby diver's pneumo hose.Also: "pneumo", "Kluge-Pneumo"
See: Pneumofathometer
Instrument to measure the depth of a diver, which measures the ambient pressure at the diver by measuring the pressure in a hose filled with air with an open end at the diver and with the surface end connected to a gas supply, control valve and pressure gauge calibrated in msw, fsw, or often both.Main article: Pneumothorax
Air or other breathing gas in the chest cavity, outside of the lung, particularly between the pulmonary pleurae, sometimes resulting in a collapsed lung.Subsection: Top, Pa, Pe, Pi, Po, Pu
Main article: pony cylinder
Relatively small scuba set, usually carried as an independent alternative breathing gas source by a recreational scuba diver.See: Positive displacement compressor, positive displacement pump
(of compressor) A configuration that compresses gas by reducing the volume of the compression chamber (eg. cylinder) by mechanical means (eg. piston) to produce higher pressure of the contents which flow out via the exhaust port, usually through a non-return valve.
May also refer to a pump in which a fixed volume is transferred during each cycle, relatively independent of inlet and outlet pressures.See: Human physiology of underwater diving#Positive and negative pressure breathing
Breathing against an external pressure slightly greater than the relaxed pressure in the lungs. More effort is needed to exhale, less to inhale. This can occur when using a positive pressure mask, front mounted counterlungs on a rebreather, or if in a steep head down position with a single-hose demand valve.See: Full-face diving mask#Positive pressure
A full-face mask which maintains an internal pressure slightly higher than external ambient pressure, necessitating slight positive pressure breathing, and ensuring that if the mask skirt seal fails, gas will leak out, rather than water leaking in, which provides a more secure airway and provides some protection against contaminated water.See: safety stop
See: Diving cylinder#Pre-fill inspection and recording of details
Examination of the external condition of a pressure vessel and fittings to ensure that it complies with requirements before accepting for filling.See: Gas blending for scuba diving#Blending nitrox
Nitrox blend supplied in bulk containers for decanting or boosting for direct use, or with high oxygen content used to blend nitrox of lower oxygen content by topping up the decanted pre-mix with air.Also: pressure sensor
Main: Pressure transducer
A component that produces an output signal proportional to a pressure input, which can be processed to give an output indicating the pressure. Used in dive computers, electronic pressure gauges, and pressure transmitters, among other uses.Also: wireless pressure transmitter
See: pressure transmitter
Pressure transducer (q.v.) with a wireless transmitter that sends a coded signal to the diver's dive computer which uses the data to display remaining cylinder pressure, which can in some applications be used to provide other gas management information.Main article: Professional diving
Also: occupational diving
Diving which is done as part of the diver's employment or professional occupation. Definitions vary in different jurisdictions.See: Wreck diving#Progressive penetration
An incremental approach to cave and wreck exploration. Each dive goes a bit further so that the divers develop a familiarity with the environment.See: Pressure relief valve
Type of safety valve used to control or limit the pressure in a system.See: Pounds per square inch
Unit of pressure in the Imperial system.See: Push-to-talk
Push to talk: Voice communication systems which require the user to press a button to transmit. Used with through water systems to conserve battery power.Subsection: Top, Pa, Pe, Pi, Po, Pu
Main article: public safety diving
The underwater work conducted by law enforcement, fire department rescue, and search & rescue/recovery dive teams.See Barotrauma
Also: POIS
Pulmonary barotrauma of ascent related diseases. Lung over-pressure injury which may manifest as arterial gas embolism, pneumothorax, tension pneumothorax, mediastinal emphysema, subcutaneous emphysema or occasionally pneumopericardium.See: Purge button
Button or flexible area on the front or side of a demand valve which allows the user to manually open the second stage valve to provide gas flow without inhalation.See: Purge valve
Also: drain valve
Non-return valve in snorkel or mask which allows water to drain either under gravity or as a result of exhalation into the air spaceSee: pendulum rebreather
Also: "Pee-valve"
See: Dry suit#The P-valve
A valved catheter fitted to a dry suit, which enables a diver to urinate at any time without having to get out of the water.See: Pyle stop
Named after Richard Pyle, an early advocate of deep stops. An additional brief deep decompression stop, typically 2 minutes long and half way between the maximum depth and the first conventional decompression stop.Main article Quadrat
See also: photo quadrat
A small, typically rectangular plot used in ecology and geography to isolate a standard unit of area for study of the distribution of an item over a large area. The quadrat is suitable for sampling plants and slow-moving or sessile animals.Subsection: Top, Ra, Re, Ri, Ro, Ru
Also: "cobra guard", valve cage
Frame attached to the top of back-mounted scuba cylinders to protect valves, manifold, and regulator first stages from impact with the surroundings.See: nitrogen narcosis
Main article: rash guard
A shirt made of spandex and nylon or polyester, worn to protect against rashes caused by abrasion, and jellyfish stings. These shirts can be worn by themselves, in tropical water, or under a wetsuit.Also: "ratio deco"
Main article: Ratio decompression
A technique for calculating decompression schedules for scuba divers engaged in deep diving without using dive tables, decompression software or a dive computer.See: Recreational Dive Planner
Subsection: Top, Ra, Re, Ri, Ro, Ru
Main article: Diving rebreather
See also: gas extender and reclaim system
Underwater breathing apparatus which recycles most of the exhaled gas, removing carbon dioxide and topping up oxygen before the gas is breathed again.Also: piston compressor
Main article: Reciprocating compressor
Compressor in which the volume of the compression chamber/s is cyclically changed by reversing linear motion. Usually a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases a raised pressure.See: Reclaim helmet
Diving helmet with a reclaim gas regulator allowing exhaled gas to be safely returned to the surface through an additional hose on the umbilical.See: Reclaim regulator
A diving regulator designed to safely return exhaled gas to a reclaim hose at lower than ambient pressure. Function is similar to a BIBS exhaust valve.See: Gas reclaim system
System for recovering helium based breathing gas used by divers and recycling it.See: Recompression
Main article: Recompression chamber
A hyperbaric chamber used to treat divers suffering from certain diving disorders such as decompression sickness.Also: "hook breathing"
See: Recovery breathing
A technique used by freedivers on surfacing to reduce the risk of surface blackout. A partial exhalation is made, followed by a quick inhalation, then the diver closes the airway and pressurises for a few seconds as if about to cough. This is repeated a few times over the first 30 seconds or so on the surface. The aim is to keep thoracic pressure slightly raised to artificially raise arterial oxygen partial pressure or prevent it from dropping in the critical seconds until newly oxygenated blood can reach the brain, and thereby prevent surface blackout. This is the same technique used by pilots during high-g maneuvers, and by mountaineers at high altitude.Main article: Recreational diving
Also: "RDP"
Main article Recreational Dive Planner
A no-stop decompression table developed by DSAT.See: algal bloom
Main article: Reduced gradient bubble model
A computationally intensive bubble model decompression algorithm developed by Bruce Wienke.See: Engineering redundancy
Technical diving philosophy of ensuring that a spare or backup is available for any item of life-support equipment that would immediately endanger the diver if it were to fail.Also: redundant gas supply, fully redundant gas supply, redundant air supply etc.
See Redundant breathing gas supply
A breathing gas supply, carried by the diver, which is both suitable for the depths at which it may be breathed, and sufficient to allow the diver to make a safe and controlled return to the surface or other place where more breathing gas is available, which is not used during the dive, and is stored in one or more cylinders which are mot the one the diver is breathing from at any given time.See Ice diving#Regulator freezing
Locking of the regulator mechanism caused by freezing of the water due to expansion cooling of the regulated air. Often causes the mechanism to lock open, causing free flow and further cooling.See Decompression practice#Repetitive dives
Any dive which is done while the tissues retain residual inert gas from a previous dive.See Scuba gas planning#Reserve pressure and Surface-supplied diving#High-pressure reserve gas
Gas which is not intended to be used during the dive, and is reserved for contingencies.See: Scuba cylinder valve#
Cylinder valve with a lever operated bypass valve to release the gas below reserve pressure.See: Decompression practice#Residual nitrogen time
Nitrogen in excess of normal atmospheric saturation remaining in the diver's tissues after a dive.Also: "RNT"
See: Decompression practice#Residual nitrogen time
Time penalty in a repetitive dive equivalent to time at depth which would produce the residual nitrogen in the diver at the start of the dive.Also: introductory dive, introductory diving experience, or trial dive
See: Introductory diving
Recreational dive by an uncertified person under the paid direct supervision of a recreational diving instructor, after a very basic training session to learn the essential safety skills in confined water. Resort dives are limited to shallow water free of significant additional hazards. No certification is gained, though the dive may count towards an entry level certification if it follows closely. Compare with try-diving and Supervised diver.Also: "minute ventilation"
Main article Respiratory minute volume
The volume of gas inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs in one minute.Main article Respiratory quotient
The ratio of carbon dioxide produced as a metabolic product to the oxygen consumed.Also: reverse ear, reverse squeeze, reversed ear.
Barotrauma of the ear caused by a middle ear gas space pressure greater than ambient pressure, or greater than the pressure in the external autitory canal, causing the eardrum to bulge outwards.See: reduced gradient bubble model
Subsection: Top, Ra, Re, Ri, Ro, Ru
See also: bungee (sidemount)
Length of shock cord with metal rings and a clip used to control the position of the top end of a sidemounted cylinder. Differs from a regular bungee in having the rings. A popular configuration is a bolt snap connected to a ring by a quick link, with a length of bungee from the ring to another quick link which is used to connect the assembly to a D-ring on the back of the harness. The bolt snap is clipped to the shoulder D-ring and the cylinder neck bolt snap is clipped to the ring.Main article Rip current
A strong localised flow of water to seaward from near the shore, typically through the surf lineMain article Drilling riser
A conduit that provides a temporary extension of a subsea oil well to a surface drilling facilitySee: respiratory minute volume
See: residual nitrogen time
Subsection: Top, Ra, Re, Ri, Ro, Ru
See: Scuba gas planning
Retention of a breathing gas reserve based on calculated values for the amount of gas required for a safe ascent from any point in the planned dive profile. Factors such as emergency supply of gas to a buddy, air consumption rates under stress and decompression gas requirements are considered in the calculations.Subsection: Top, Ra, Re, Ri, Ro, Ru
See: Rule of thirds (diving)
Cave and wreck penetration breathing gas management convention where no more than one third of the gas in a cylinder may be used on the inward part of the dive, and the other two thirds is kept for exit: One third for the planned exit, and one third in case of an emergency.Also: "positive reserve valve", "automatic valve", or "calibrated orifice"
A cylinder valve which limits the outflow by a calibrated orifice when in the "on" position.Subsection: Top, Sa, Se, Si, So, Su
See: surface air consumption rate
See: Decompression practice#Safety stop
A voluntary (not required by the decompression schedule) additional decompression stop intended to further reduce risk of decompression sickness.Main article: Salt water aspiration syndrome
A reaction of the lungs to inhalation of a mist of salt water.See: Decompression theory
Condition where the inert components of the breathing gas dissolved in a diver's tissues are in equilibrium with the gas in the lungs.Main article: Saturation diving
Diving mode where the divers remain pressurised for long enough for the slowest tissues to saturate with the inert components of the breathing gas, usually for periods of several days or weeks, and decompress only at the end of the period. Decompression from saturation is controlled only by the slowest tissue.Main article: Saturation diving system
The combination of equipment and services to operate a saturation diving project. It would include the closed diving bell, the accommodation modules, decompression chamber, life-support systems, gas storage and supply systems, pressurisation equipment, underwater breathing apparatus, and launch and recovery systems. In may also include a hyperbaric evacuation system.Subsection: Top, Sa, Se, Si, So, Su
Main article: Schrader valve
Valve using a standard automotive tyre valve insert, common in low pressure inflation hose female connectors and BC inflation valves.Main article: Scientific diving
Diving for purposes of scientific research. The rules and constraints of scientific diving vary in different jurisdictions, but generally allow different options to mainstream commercial diving.Main article: Carabiner
A clip mechanism which can be locked in the closed position by turning a threaded barrel.See: Rebreather#Carbon dioxide scrubber
Canister containing material (sorb) which chemically combines with carbon dioxide to remove it from the gas passed through the canister.Main article: Scuba set
Self-contained underwater breathing apparatus. May be open or closed circuit.Also: Underwater orienteering
Main article: Scuba orienteering
Competitive underwater sport in which scuba divers attempt to swim a circuit marked by buoys, without surfacing, using compass navigation and mechanical distance measurement. Points are awarded for time and accuracy according to the specific course definition and length.See: Scuba replacement
Mobile surface-supplied diving equipment using portable gas storage cylinders for primary and reserve breathing gas supply. Preferred to scuba for commercial diving applications due to lower perceived risk compared to scuba, and because equipment and procedures are otherwise identical to surface supplied diving using compressors for air supply. Used when logistical constraints or air quality issues preclude use of a compressor.Subsection: Top, Sa, Se, Si, So, Su
See: Underwater searches
Cord used to indicate the transect for a search. The diver moves along the line, searching by sight or feel on one or both sides of the line. After the transect has been searched, the line is moved to the next transect. usually a short distance offset from the previous position, at a distance which depends on the visibility and the size of the target.See: Underwater searches
Systematic procedure for covering the search area sufficiently to be reasonably sure of finding a given target if it is there. Several patterns are in general use for underwater searches, depending on the target, the terrain, and available facilities.Main article: Secondary drowning
A complication of aspiration of water or other fluids into the lungs.See: backup regulator
See: demand valve
The part of a diving regulator which provides pressure reduction from intermediate pressure to ambient pressure on demand. Demand valve.Also: "hyperbaric lifeboat" (HLB), "hyperbaric rescue vessel" (HRV)
A pressure vessel adapted for use as a means of hyperbaric evacuation, and fitted to a conventional lifeboat hull.See: Diving suit#Semi-dry suit
A wet suit with wrist and ankle seals, and usually a more watertight zipper than usual, to reduce flushing of water through the suit.Main article: Vapor–liquid separator
Device which facilitates the separation of liquid particles from the compressed gas, usually with a drain to periodically remove accumulated liquid from the system.See: Decompression theory#Diffusion limited tissues and the "tissue slab", and series models
A decompression model based on the assumption that diffusion is the limiting mechanism of dissolved gas transport in the tissues, in which there is perfusion transport for one compartment, and diffusion between a series of compartments,Main: Serial number
See: Rebreather diving#Set-points
Reference value for oxygen partial pressure in an electronically controlled closed circuit rebreather. The control system monitors the real time value of oxygen partial pressure in the breathing loop and automatically adjusts the composition by adding gas to keep the concentration between the upper and lower set-points.See also: SAC
Surface Gas ConsumptionSubsection: Top, Sa, Se, Si, So, Su
See: bungee cord
Main article: Diving shot
A rope between a float at the surface, and a sufficiently heavy weight holding the rope approximately vertical.Subsection: Top, Sa, Se, Si, So, Su
Main article: Sidemount diving#Terminology
A scuba diving equipment configuration which has diving cylinders mounted alongside the diver, below the shoulders and along the hips, instead of on the back of the diver.See: Sidemount diving#Terminology
The practice of using sidemount configuration (bungee loops and/or butt-plate rails) as a means for stowing stage/deco cylinders when otherwise diving in back-mounted scuba.See: Scuba skills#Entries
An entry technique which minimises noise and splash, suitable for entry from a low platform. The diver sits with feet dangling over or into the water, turns their torso sideways, takes their weight on their hands, then swings off the surface and drops feet first into the water, slowed by their arms, and lets go with the hands when in the water.: 251Main article: Silica gel
A desiccant filter medium used to adsorb water.Main article: Silt out
A situation when underwater visibility is rapidly reduced to zero, usually when a diver disturbs silt deposits.See: Cave diving#Equipment
Device which is inserted into silt or sand to provide an anchor point, such as for a tie-off on a cave line. Silt screws are generally stakes made from small bore plastic (PVC) pipe with a sharpened end.Main article: Single buoy mooring
A loading buoy anchored offshore, that serves as a mooring point and interconnect for tankers loading or offloading gas or liquid products. SPMs are the link between geostatic subsea manifold connections and weathervaning tankers. They are capable of handling any size ship, even very large crude carriers (VLCC) where no alternative facility is availableMain article: Sinkhole
A natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks – or suffosion processes for example in sandstoneMain article: Sintering
Particulate or granular material bonded together by the application of pressure and sufficient heat to partially melt the surface of the particles and weld them together. The product is usually porous.Main article: Skandalopetra diving
A flat stone, usually of marble or granite, weighing between 8 and 14 kg, with rounded corners and edges, and tied to a rope, historically used by Greek sponge free-divers to assist descent. When the diver wishes to ascend the rope is used to signal the tender on the boat who then pulls in the rope. Currently skandalopetra diving is a competitive sport.See: dive skins
See: Skip breathing
Breathing pattern where the diver holds each breath a while to conserve breathing gas, which can cause hypercapnia which can lead to headaches, aggravate nitrogen narcosis, increase risk of oxygen toxicity, and reduce physiological reserves in an emergency.See: Submarine pipeline#The S-lay system
Method of laying undersea pipelines by welding the sections together on the lay barge and deploying them from the stern horizontally guided by a "stinger" - a structure that supports the pipe string to control its bend radius. The term refers to the shape of the bend in the pipe which transitions from roughly horizontal onboard where the sections are welded together, to angled downward over the stinger, to roughly horizontal again as it settles on the seabed.Also: diver's slate and wrist slate
See also: Slate (writing)
Rigid hard plastic tablet used for writing messages or notes underwater. Compare with wet notes. Usually with a slightly roughened surface to accept pencil marks.See: Diving cylinder#Open-circuit
Independent cylinder with its own regulator carried clipped to the harness at the side of the diver. Compare with sidemount, and stage cylinder.See: Y-valve
See Scuba cylinder valve#Dual outlet valves
A cylinder valve with two valved outlets angled to left and right of the centrelineSee: surface marker buoy
See: Shackle#Snap shackle
A clip connector mechanism which locks when closed, can be operated without tools, and can usually be released under load.See: Rubber band#Snoopy loop
A heavy duty elastic band made from a slice of inner tube.See: Underwater photography#Snoot
Accessory for a photographic strobe which limits illumination of the subject to a very small area, leaving the background datk, and virtually eliminating backscatter.Main article: Snorkel (swimming)
Tube with a bend and mouthpiece used for breathing air from above the water surface when the wearer's mouth and nose are submerged.Main article: Snorkeling
Swimming at the surface of the water while breathing through a snorkel. the snorkeller is almost always equipped with a diving mask or swim goggles, and usually swimfins.See: Snorkel (swimming)#Independent snorkel construction
Device to hold a snorkel in place at the side of a diving mask by fixing it to the mask strap.See also: Hookah
Main article: Snuba
Snuba is a portmanteau of "snorkel" and "scuba", referring to a proprietary recreational surface supplied underwater breathing system supplied from a cylinder mounted on a small raft towed by the diver.Subsection: Top, Sa, Se, Si, So, Su
Main article: Solo diving
The practice of scuba diving alone, without a dive buddy or in-water standby diver.See: Choked flow
Metering device to provide constant mass flow of a gas.Also: "sodasorb", "sodalime" and "sofnolime"
See" Diving rebreather#Carbon dioxide scrubber
Carbon dioxide absorbent material used in rebreather or life support system scrubber to remove carbon dioxide from the breathing gas so it may be recycled.Subsection: Top, Sa, Se, Si, So, Su
Main article: Speargun
Hunting weapon for shooting fish underwater which propels a barbed steel spear a short distance forward using stored energy from stretched rubber strips or compressed air behind a captive piston.Also: "helium unscrambler" and "unscrambler"
See: Diver communications#Equipment
An electronic device to render words spoken in a hyperbaric helium environment intelligible.Main article: Speleogen
Dissolution features in bedrock.Main article: Speleothem
Also known as a cave formation: A secondary mineral deposit formed in a cave.See: submersible pressure gauge
See: Self-propelled hyperbaric lifeboat
See: Full-face diving mask#Straps
Mask strap system for full-face masks with three or more straps. (commonly 5)See: Standard diving dress#Helmet
A valve in the side of a copper diving helmet which could be used by the diver to suck in a mouthful of seawater to spit onto the inside face of a viewport to wash off condensation droplets to improve their view.See: single point mooring
See: Spring (hydrology)
Place where a concentrated flow of water emerges from the ground.See:Swimfin#Attachment
Fin strap using a stainless steel spring to secure the fin to the foot.See: Dive profile#Square profile
Dive profile where the diver descends continuously to the maximum depth and stays there for the duration of the dive before ascending directly at a stedy rate to the surface or first decompression stop. This profile provides worst case exposure for gas absorption by the body tissues for a given depth and bottom time, and is assumed for most decompression planning using decompression tables.See: barotrauma
Injury or discomfort caused by increase of ambient pressure above the pressure in a gas space in contact with the diver's body, causing a pressure difference tending to squeeze body tissues into the lower pressure volume of the gas space. A cause of several kinds of barotrauma.Subsection: Top, Sa, Se, Si, So, Su
See: buoyancy compensator
See: Stage cylinder
See: Staged decompression
The practice of making decompression stops.See: stage-drop
Placing a stage cylinder at the distance line for planned later use.See: Sidemount diving#Terminology
The use of standard deco/stage cylinder configuration, without back-mounted cylinders, on an otherwise standard, or partially modified tec/rec BCD. The cylinders are attached to waist and shoulder D-Rings by direct bolt-snap, and no bungee cord is used in the upper attachment. Similar to, and may be confused with sidemountSee: stage rigging (scuba)
The clips, straps and cords fastened to a scuba cylinder which are used to mount it as a stage cylinder.See: Stage set (scuba)
A scuba set to be used during a specific stage of a dive. Often rigged and carried as a sling mount or sidemount set. Sometimes dropped at the end of the outward leg of the stage, and retrieved on the return to complete the return leg of the same stage.Also: "heavy gear"
Main article: Standard diving dress
Early free flow surface supplied diving equipment using a heavy rubberised canvas suit, copper helmet and corselet, and weighted boots. Still in use in some parts of the world.See: Standard diving dress#Helmet, Diving helmet#Standard diving helmets (Copper hats)
The copper and brass free-flow diving diving helmet used with standard diving dress.Main article: Standard operating procedure
Procedure compiled by an organisation prescribing the processes to be followed when performing specified tasks.See: Standby diver
(Professional) diver functioning as a safety backup to the working diver. Often on the surface at the dive control point, but ready to enter the water at very short notice on the instruction of the supervisor. In bell diving the stand-by diver would be the bellman.Main article: Static apnea
Underwater breath-holding without changing locationAlso: "hydrostatic imbalance", "SLL"
The pressure difference between gas inside the lungs and the gas inside the mouthpiece of the breathing apparatus or inside the helmet. In most rebreathers this is the hydrostatic pressure at depth of the counterlung. In ballasted bellows counterlungs the pressure is modified by the force exerted by the ballast weight.See: decompression stop
Also: "living depth"
See: Saturation diving#Accommodation
Depth pressure in a saturation system at which divers live between compression and decompression when not locked out on a dive.Also: "giant stride entry"
See: Scuba skills#Entries
Entry technique from a platform a small to moderate distance above the water surface, which is suitable to stand on before entry. The diver faces the water and steps out with the leading foot, pushing away from the platform with the back foot, and drops into the water while maintaining a vertical posture until fully submerged. It is usually advisable to hold loose equipment against the body, particularly the mask and DV, and if there is no crotch strap, the buoyancy compensator is held to prevent it riding up the torso on impact. The feet can be brought together after initial impact to limit depth of immersion in moderately shallow water, by applying fin thrust downwards.Subsection: Top, Sa, Se, Si, So, Su
See: Subcutaneous emphysema
Gas under the skin resulting from lung overpressure injury.See: closed bell
A closed diving bell, used for transferring divers under pressure to and from the worksite. Particularly if used for decompression.Also: "SPG"
See: Submersible pressure gauge
Gauge attached to the first stage regulator and used to monitor pressure remaining in the diving cylinder.See: Dry suit#Over-inflation
Excessive inflation of a dry suit leading to uncontrolled ascent.Main article: Sump (cave)
A passage in a cave that is submerged under water.See: Superoxide scrubber
Rebreather scrubber which not only removes carbon dioxide from the exhaled air, but also replenishes the oxygen by chemical reaction with potassium superoxide.See: Supersaturation
A temporary and thermodynamically unstable condition of a solvent containing more dissolved gas than it can hold in solution over the long term for the prevailing conditions. A necessary condition for bubble growth in decompression sickness.Main article: Supervised Diver
EN 14153-1 / ISO 24801-1 standard competence for recreational scuba diver. The level 1 "Supervised Diver" has sufficient knowledge, skill and experience to dive, in open water, to a recommended maximum depth of 12 m, which do not require in-water decompression stops, under the direct supervision of a dive leader, in groups of up to four level 1 scuba divers per dive leader provided the dive leader is capable of establishing physical contact with all level 1 scuba divers at any point during the dive, only when appropriate support is available at the surface, and under conditions that are equal or better than the conditions where they were trained.See: diving supervisor
See: Supply lock
Small lock on a saturation life support habitat for transfer of relatively small items.See: Support diver
A voluntary member of a technical diving team who acts as a stand-by diver to the primary dive team, or provides in-water logistical support for a dive.See: surface decompression
See: Breaking wave
The mass or line of broken water formed by waves breaking on a shore or reefSee: Decompression practice#Surface decompression
A procedure in which some or all of the staged decompression obligation is done in a decompression chamber immediately after surfacing instead of in the water.See also: free gas volume
Gas volume calculated as expanded to surface pressure.See: Decompression practice#Surface interval
The time spent by a diver at surface pressure after a dive during which inert gas which was still present at the end of the dive is further eliminated from the tissues.Also: "SMB"
Main article: Surface marker buoy
A buoy towed by a diver to indicate the diver's position to people at the surface.See: Waves and shallow water
Reciprocating water movement parallel to the bottom surface caused by the passing of a wave overhead, by analogy with the transient linear motion of a ship in the direction of travel also called surge.Main article: Sustained load cracking
The development of cracks in a material subjected over long term to static stress significantly less than the yield stress. There is a low but significant risk of this mode of failure in pressure vessels of AA6351 aluminium alloy.Main article: Swell (ocean)
A series of surface gravity waves that is not generated by the local wind.Owlapps.net - since 2012 - Les chouettes applications du hibou