See the Outline of underwater diving for a hierararchical listing of underwater diving related articles grouped by topical relevance
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.
Surface-supplied divers riding a stage to the underwater workplace
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:
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 reaction
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 tissue
(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.[1]
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.[2]
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.
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.[3]
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 space[4]
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.[2]
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.[8]
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.[9]
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.[1]
pigtail
Coiled section of pipe to provide greater flexibility.
Standard connection type for portable medical oxygen cylinder valves and regulators.[10]
pinnacle
A distinct local high point on a reef, similar to a geological pinnacle, but usage is somewhat looser, and may refer to a large boulder on top of a outcrop, or the tallest in a cluster of high points. In many cases the exact topography is unknown as it has not been seen or surveyed in high enough resolution. The term usually implies a submerged feature but has also been applied to exposed and half-tide rocks.
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.[14]
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.[1][15]
Air or other breathing gas in the chest cavity, outside of the lung, particularly between the pulmonary pleurae, sometimes resulting in a collapsed lung.
Relatively small scuba set, usually carried as an independent alternative breathing gas source by a recreational scuba diver.
P-port
A large bore airtight quick connector fitting designed and used by Dräger on diving and firefighting breathing apparatus, for ambient pressure breathing gas connections, which has been used in rebreathers, particularly modifications, and full-face masks. Part of the Dräger P-connector system.[16]
(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.[17]
May also refer to a pump in which a fixed volume is transferred during each cycle, relatively independent of inlet and outlet pressures.
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.
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.[18]
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.
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.[20]
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.
primary light
The main light to be used on a dive. Usually the most powerful.[21][22]
primary regulator
the regulator which the diver intends to breathe from for most of the dive. Particularly when diving with back-mounted manifolded twin cylinders.
primary tie-off
First tie off of the guideline in a penetration dive. This is usually made in a place with free vertical access to the surface.[23]
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.
The underwater work conducted by law enforcement, fire department rescue, and search & rescue/recovery dive teams.
pull
1.A relatively long pull on a lifeline when used for rope signals. (see "bell" for comparison).[11]
2.Part of an ascent between the bottom and a decompression stop, between decompression stops, or to the surface.[25] Possibly deriving from the practice of the diver's tender pulling a surface-supplied diver up by the umbilical or lifeline, and stopping the ascent at the depths planned for staged decompression.
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.[26]
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.[27]
purge valve
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 space
push gradient
Tech diving jargon: Decompress at a high gradient factor, particularly when exceeding the baseline M-value. This will expose the diver to a higher risk of developing decompression sickness while reducing time decompressing in the water.[29]
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.[31]
Oval connector shaped like a chain link with a screw gate on one side.
quad
A group of high pressure gas storage cylinders mounted upright on a rectangular frame and manifolded together. Usually in 4, 6, 9, 12, or 16 cylinder arrangements.[32]
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.
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.
Rat hat
Ratcliffe diving helmet, Designed by Bob Ratcliffe (engineer), later produced by Oceaneering International. No longer in production.[33]
A technique for calculating decompression schedules for scuba divers engaged in deep diving without using dive tables, decompression software or a dive computer.[34][35]
Underwater breathing apparatus which recycles most of the exhaled gas, removing carbon dioxide and topping up oxygen before the gas is breathed again.[36]
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.[37][38]
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.[40]
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.[47][48]
1.Recreational diving may be considered to be any underwater diving that is not occupational, professional, or commercial, in that the dive is fundamentally at the discretion of the diver, who dives either to their own plan, or to a plan developed in consensus with the other divers in the group, though dives led by a professional dive leader or instructor for non-occupational purposes are also legally classified as recreational dives in some legislations.[49][50][51]
2.Recreational diving or sport diving is a type of diving that uses scuba equipment for the purpose of leisure and enjoyment. In some diving circles, the term "recreational diving" is used in contradistinction to "technical diving", a more demanding aspect of the sport which requires greater levels of training, experience and equipment. In other circles, technical diving is considered a subset of recreational diving as opposed to "professional diving", which is done as part of the diver's work.
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.[56]
redundant breathing gas supply
Also: redundant gas supply, fully redundant gas supply, redundant air supply etc.
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.[57]
redundant equipment
duplicated or spare equipment carried by the diver or team to substitute for vital primary equipment in case of a malfunction. In some cases, such as cave lights, multiple redundancy may be desirable. A redundant breathing gas supply is the most common example.[58]
A ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water.In recreational diving the term is also used for a slope or outcrop of similar material, or an artificial reef.
reef dive
reef diving
Dive at a reef site. Possibly the most common type of recreational dive site types. Coral reefs may be more popular as diving destinations, but rocky reefs are probably more globally widespread. Reef topography ranges from relatively flat to vertical walls and overhangs, which may include caves and other overhead environments.
reel
Mechanism used to store, deploy and recover long lengths of line at low tension.
reference temperature
Temperature at which a cylinder may be safely and legally filled to the nominal charging pressure without corrections.[19]
regulator
1.A mechanism for controlling the output pressure of a high pressure gas supply.
2.As 1, with a demand valve (q.v.) incorporated which provides the diver with breathing gas at ambient pressure.
regulator changeout
regulator swap-out
Scuba emergency skill of swapping a correctly functioning regulator with one that is malfunctioning to gain access to breathing gas in a cylinder while underwater. Usually applied to side- or sling-mounted cylinders.
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.[59]
reject criteria
rejection criteria
Features, states or conditions which are not acceptable.[19]
Any dive which is done while the tissues retain residual inert gas from a previous dive.[45]
repet-up
Commercial diving term for a type of multilevel dive, in which the depth is decreased over elapsed time, with the purpose of allowing a longer useful dive time and minimising decompression time.[60]
Repex
Method of estimating tolerable repetitive exposure to high partial pressure oxygen.[61]
rescue tether
A short lanyard or strap carried by a surface supplied stand-by diver to be used to tether an unresponsive diver to the standby diver during a rescue. It is attached at one end to a D-ring on the stand-by diver's harness, and has a clip at the other end which may be secured to a D-ring on the casualty's harness to allow the rescuer the use of both hands during the return to the bell or surface.
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.
The ratio of carbon dioxide produced as a metabolic product to the oxygen consumed.
restriction
Section of a cave which is difficult to pass through due to lack of space. A minor restriction is too small for two divers to swim through together, a major restriction requires the diver to remove equipment to fit through.
revalidation
Certification that an item of equipment continues to be fit for service. Usually after passing the required periodic inspection and testing by an approved or authorised practitioner.
reverse block
Blockage of a sinus or eustachian tube preventing relatively high internal gas pressure from escaping. [63]
reverse ear squeeze
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.[63]
reverse jump
Procedure to cross a gap during an exit which allows the line to be retrieved without returning to the start point. In the event of a line break or removed primary reel, one diver holds the end of the search line at the break point, and the other searches for the other part of the broken line or the exit while laying line from the reel. When the original line or exit is found, the reel handler signals to the static diver with line pulls and the static diver swims in the direction of the line while the reel handler reels it in, recovering the line.[64]
reverse profile
reverse dive profile
Repetitive dive which is deeper than the previous dive.[65]
Multilevel dive in which a later level is deeper than an earlier level.[66]
Length of shock cord with metal rings and a clip used to control the position of the top end of a sidemounted cylinder.[67] Differs from a regular bungee in having the rings.[67] 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.
Footwear worn over a dry suit with integral socks suitable for walking on hard and rough surfaces and for wearing with fins. They can also be worn over neoprene socks with a wetsuit.[68]
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.
roll-off
Closing of a cylinder valve as a result of scraping contact between the valve knob and the overhead or other surroundings. The left hand knob is more likely to roll-off, closing the backup regulator in the standard twins configuration. Roll-off is an emergency if the diver does not have an immediately accessible alternative breathable gas supply.[64]
Member of the drilling crew who works under the direction of the driller to make or break connections as drillpipe is tripped in or out of the hole.[11]
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.[69]
run line
running line
Unreeling line under light tension while advancing. Usually in the context of laying a distance line.
run time
Time elapsed since the start of a dive.
running stop
A pause made during ascent to adjust the average ascent rate to the nominal value. For example a nominal ascent rate of 3m per minute might use an actual ascent rate of about 5m per minute and make a stop every 3m until the end of the current minute, resulting in a slightly stepped profile with an overall ascent rate corresponding to the nominal rate.[34]
run time schedule
Decompression schedule and dive plan based on elapsed time from the start of the dive, All waypoints and events are specified in terms of elapsed time with start of descent at zero.
R-valve
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.[70]
Item of equipment or process with the purpose to prevent or limit the consequences of a high risk hazard, that if realised, could result in the fatality or severe injury of one or more divers or support crew.[1]
safety reel
Reel with relatively short line for use in an emergency, usually for searches to find a lost buddy or lost guideline or to jump a line break.[64]
safety spool
Spool with relatively short line for use in an emergency, usually for searches to find lost buddy or lost guideline or to jump a line break.[64]
A voluntary (not required by the decompression schedule) additional decompression stop intended to further reduce risk of decompression sickness.[71][72]
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.[75][76]
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.[77]
Self-contained breathing apparatus. The broader class of breathing apparatus carried by the user. Conventional usage usually refers to equipment which is not intended for underwater use, but scuba (originally self-contained underwater breathing apparatus) is technically a subclass of SCBA. Compare with breathing apparatus (BA) and underwater breathing apparatus (UBA).
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.
D-ring on scuba harness used to attach to scooter tow line. Usually on front of the harness crotch strap.[64]
SCR
1.Semi-closed circuit rebreather: A rebreather (q.v.) which either dumps part of each breath to the environment or continuously adds gas and dumps the excess. Compare with closed circuit rebreather (CCR) (q.v.).
2.Surface Consumption Rate - An alternative term with the same meaning as Surface Air Consumption (SAC) (q.v.). Not to be confused with Semi-closed Circuit Rebreather.
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.
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.[1]
S-drill
Safety drill. An air sharing exercise based on deploying the long hose primary regulator.
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.
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.
Device which facilitates the separation of liquid particles from the compressed gas, usually with a drain to periodically remove accumulated liquid from the system.
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,
1.Number stamped on the cylinder by the manufacturer in the shoulder area which identifies the cylinder. In combination with the manufacturer’s identification this will be unique to the cylinder.[19]
2.Character string, including number, marked on an item of equipment by the manufacturer to uniquely identify it.
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.[79][80]
Loss of consciousness during a dive associated with occurrence at a shallow depth. Used for several different mechanisms, depending on context, therefore often leading to confusion.
1.See: Shallow-water blackout
Loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five metres (16 feet), when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it.[81]
2.See: Freediving blackout#Terminology and latent hypoxia
Loss of consciousness caused by cerebral hypoxia at the end of a deep breath-hold dive during the latter part of the ascent or immediately after surfacing due to lowered pO2 caused by reduction in ambient pressure, see also latent hypoxia.
3.Loss of consciousness while ascending on a rebreather due to sudden drop of pO2 in the breathing loop, usually associated with manual CCR and SCR.
shark pod
shark shield
Electrical device carried by a diver intended to repel sharks by electrical field pulses.[82]
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.[84]
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.[85]
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.[86]:251
Device which is inserted into silt or sand to provide an anchor point, such as for a tie-off on a cave line.[67] Silt screws are generally stakes made from small bore plastic (PVC) pipe with a sharpened end.
simultaneous operations
Two or more potentially clashing operations occurring, for example, at the same time and same location.[1]
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 available[11]
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 sandstone[89][90]
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.[91][92]
siphon
Place where water from a stream flows into the ground. also "swallow hole"[12]
A flat stone, usually of marble or granite, weighing between 8 and 14kg, 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.[93][94]
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.[95]
skirt
1.The body of a diving mask providing a watertight seal between the lens and the face.[96][97]:4–17
2.The jacket and trouser waist flaps of a two-piece dry suit, which are overlapped and rolled together to provide a watertight seal.[30]:Ch. 1
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.[98] 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.
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.
Accessory for a photographic strobe which limits illumination of the subject to a very small area, leaving the background datk, and virtually eliminating backscatter.
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.
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.
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.[100]
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.[101]
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.[105]
1.See: Distance line#Spools
Circular device for storing line, comprising a short tubular section with a relatively large flange at each end. No moving parts. A small, compact, economical and reliable alternative to a reel for relatively short lines.[106]
2.Short, straight section of pipe or tube with a flange at each end. Also a wider range of short weldments for various purposes as components of a piping system assembled from sections of pipe, flanges and other fittings.[107]
spread
The topside base for (usually) surface supplied commercial diving operations. Also "air spread" and "saturation spread" (q.v.) depending on the diving mode.[108]
Fin strap using a stainless steel spring to secure the fin to the foot.
spring suit
A wetsuit that covers the torso and has short sleeves and long or short legs
spud
spud pile
1.A vertical steel shaft like a pile, temporarily or permanently driven into the seabed to maintain the lateral position of a barge or structure
[110][111]
2.A short rigid column driven into the ground and then removed to make a hole to initiate driving a pile, or to break through a hard layer.[111]
spud can
The foot on a leg of a Jack-up rig oil platform designed to spread the load so that the rig does not sink too deeply into the sea-bed.[11] Commonly a wide shallow conical disc structure to support the weight, with a penetrating central tip to resist lateral sliding, though details vary.[112]
spud well
spud pocket
A vertical sleeve for a spud that is attached to a spud barge to support and guide a mooring spud on a barge.[113]
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.[114]
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.
1.A cylinder used for a stage of a long penetration dive, also known as drop cylinder when it is placed on the distance line to be collected on the return. The term may be used for the cylinder and rigging with or without a regulator[115]
2.Also generically and loosely used to refer to decompression gas cylinders, bailout cylinders, travel gas, or bottom gas carried as sling cylinders (q.v.)[115]
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 sidemount[116]
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.
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.[43]
(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.[1]
Underwater breath-holding without changing location[119]
static lung load
Also: "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.[120]
steamer
A full one piece Wetsuit that covers the torso and the full length of the arms and legs.
stinger
An overboard extension at the stern of an offshore pipe lay barge used to provide additional support at the over bend of an S-lay during offshore construction.[98]
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.[122]
stroke
Derogatory term used by DIR zealots to describe divers who do not follow DIR procedures and use DIR approved equipment and configurations.
Gauge attached to the first stage regulator and used to monitor pressure remaining in the diving cylinder.[78]
suicide clip
Derogatory term for clip mechanisms which are capable of clipping onto a line or other object without the active and intentional intervention of a user.
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.
supersaturation limit
The theoretical pressure ratio between tissue gas concentration and ambient pressure above which the probability of bubble formation is unacceptably high.[2]
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 12m, 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.[125]
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.
The mass or line of broken water formed by waves breaking on a shore or reef
surface air consumption rate
A measure of air consumption in units of pressure over time, usually psi/minute, adjusted to surface pressure, used to estimate air endurance of a cylinder of specific size. Useful for those who work in imperial units.[126] SAC has a constant value for a given diver and represents gas used on the surface at rest.[127] Surface gas consumption (SGC) is an alternative term referring to alternative breathing gas mixtures. Occasionally also termed surface consumption rate (SCR)[128][129]
surface compression chamber
A hyperbaric chamber for surface use for routine decompression or therapeutic recompression.[43]
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.
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.
A buoy towed by a diver to indicate the diver's position to people at the surface.
surface orientated diving
Any diving operation in which the diver is decompressed to surface pressure after the dive. Compare to saturation diving .[43]
SURG
Southern Underwater Research Group. An organisation based in Cape Town, which publishes marine ecology field guides, dive travel guides and underwater maps.[131]
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.
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.[132]
A series of surface gravity waves that is not generated by the local wind.
swim line
Line used to space divers across the search area for a swim line search. Each diver holds the line at a distance from the previous diver of somewhat less than twice the visibility distance. The line is used to keep the divers spaced evenly across the search area while swimming perpendicular to the line.
swimthrough
swim-through
A submerged arch or short tunnel that a diver can swim through without needing to remove equipment. It is usually possible to see natural light at the far end in good visibility and illumination. Usually refers to a natural formation. Technically an overhead environment, but usually with no risk of getting lost, though entrapment may be possible.
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South African National Standard SANS 10019:2008 Transportable containers for compressed, dissolved and liquefied gases - Basic design, manufacture, use and maintenance (6thed.). Pretoria, South Africa: Standards South Africa. 2008. ISBN978-0-626-19228-0.
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Walker, J R. III; Murphy-Lavoie, Heather M. (11 January 2021). "Diving Rebreathers". Treasure Island, FL: StatPearls Publishing. PMID29494076. Retrieved 11 May 2021.
Krack, Kirk; Stepanek, Martin; Cruickshank, Mandy-Rae (2006). Lindholm, P.; Pollock, N. W.; Lundgren, C. E. G. (eds.). Safety techniques and problem management in recreational and competitive freediving(PDF). Breath-hold diving. Proceedings of the Undersea and Hyperbaric Medical Society/Divers Alert Network 2006 June 20–21 Workshop. Durham, NC: Divers Alert Network. pp.82–95. ISBN978-1-930536-36-4. Retrieved 27 January 2017.
"The Diving at Work Regulations 1997". Statutory Instruments 1997 No. 2776 Health and Safety. Kew, Richmond, Surrey: Her Majesty's Stationery Office (HMSO). 1977. Retrieved 6 November 2016.
"Diving Regulations 2009". Occupational Health and Safety Act 85 of 1993 – Regulations and Notices – Government Notice R41. Pretoria: Government Printer. Archived from the original on November 4, 2016. Retrieved November 3, 2016– via Southern African Legal Information Institute.
Campbell, Ernest S (30 April 2009). "Reduced gradient bubble model". Scubadoc's Diving Medicine. Retrieved 12 January 2010. – Bruce Wienke describes the differences between RGBM and VPM
Mount, Tom (August 2008). "9: Equipment Configuration". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1sted.). Miami Shores, Florida: International Association of Nitrox Divers. pp.91–106. ISBN978-0-915539-10-9.
Ward, Mike (9 April 2014). Scuba Regulator Freezing: Chilling Facts & Risks Associated with Cold Water Diving (Report). Panama Beach, Fl.: Dive Lab, Inc.
Roberts, Fred M. (1963). Basic Scuba: Self contained underwater breathing apparatus: Its operation, maintenance and use (2nded.). New York: Van Nostrand Reinholdt.
Gerrard, Steve Penn (11 November 2015). "Glossary". The Cenotes of the Riviera Maya 2016. Page Publishing Inc. ISBN9781682134023. Retrieved 6 April 2017.
Lang, M.A.; Lehner, C.E. (2000). Proceedings of Reverse Dive Profiles Workshop. Smithsonian Institution, Washington D.C.: American Academy of Underwater Sciences. p.28.
Edmonds, C.; McInnes, Sophie; Bennett, Michael (2005). "Reverse dive profiles: The making of a myth". South Pacific Underwater Medicine Society Journal. 35: 139–143.
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Department of Labour (11 January 2002). Diving regulations 2001 of the Occupational Health and Safety Act 85 of 1993. Government Gazette, Republic of South Africa, Regulation Gazette No. 7243. Vol.438. Pretoria: Government Printer.
British Sub-Aqua Club members (1982). British Sub-Aqua Club Diving Manual (10thed.). Ellesmere Port, Cheshire: British Sub-Aqua Club. p.567. ISBN978-0950678610.
Cheshire, William P; Ott, Michael C (2001). "Headache in Divers". Headache: The Journal of Head and Face Pain. 41 (3): 235–247. doi:10.1046/j.1526-4610.2001.111006235.x. PMID11264683. S2CID36318428. Carbon dioxide can accumulate insidiously in the diver who intentionally holds the breath intermittently (skip breathing) in a mistaken attempt to conserve air
NOAA Diving Program (U.S.) (December 1979). Miller, James W. (ed.). NOAA Diving Manual, Diving for Science and Technology (2nded.). Silver Spring, Maryland: US Department of Commerce: National Oceanic and Atmospheric Administration, Office of Ocean Engineering.
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