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:
A form of decompression sickness originally observed among Polynesian island natives who habitually did multiple repetitive deep breath-hold dives.[1][2]
A multiplicity of responsibilities leading to an increased risk of failure on the part of the diver to undertake some key basic function which would normally be routine for safety.[3]
A constant tension wire from a vessel to a weight on the seabed used as a reference to detect movement of a dynamically positioned vessel from the reference point.[4]
An extension of the scope of recreational scuba diving to applications with greater technical complexity and higher inherent risk. Definitions vary, but diving with multiple breathing gases, helium based gases, closed circuit rebreathers, or under extensive overheads are generally considered as technical diving. There is no sharp distinction from other forms of recreational diving.[5]
tech ring
D-ring welded to a belt slide so that it can not fold down against the webbing. Intended to make it easier to fit and remove snaps.[6]
An array of temperature sensors mounted in a rebreather scrubber canister along the path of gas flow to monitor the temperature as an indication of the advance of the exothermic reaction front of the scrubber, providing an indication of scrubber depletion.[7]
A vertically moored floating structure normally used for the offshore production of oil or gas, particularly suited for water depths between 300 and 1500 meters. The platform is permanently moored by means of near vertical tethers at each of the structure's corners and virtually all vertical motion of the platform is eliminated.[8]
Diagnostic procedure for decompression sickness. The diver is recompressed, and if the symptoms reduce, it may be assumed that the diver has decompression sickness and hyperbaric treatment will be effective. The test is not entirely reliable[9]
Pressure at which a pressure vessel such as a gas storage cylinder or hyperbaric chamber will be hydrostatically tested for revalidation. Usually 1.5 or 1.67 x working pressure for gas storage cylinders.[10]
Ascent controlled by a line from the diver to a fixed point at the bottom. This may be used to control depth and rate of ascent when the diver has inadvertently lost complete control of buoyancy due to loss of ballast weight, so cannot attain neutral buoyancy at some point during the ascent, and needs to do decompression. CMAS require this skill for their Self-Rescue Diver certification.[11]
tethered diving
Diving with a lifeline between the diver and a surface tender.[12]
tether management system
Also: TMS
The TMS is either a garage-like structute which contains and supports the ROV during lowering through the splash zone or, on larger work-class ROVs, a separate assembly mounted on top of the ROV. The purpose of the TMS is to lengthen and shorten the tether so the effect of cable drag where there are underwater currents is minimized.[13]
A procedure for treating decompression sickness by recompressing the diver, thus reducing bubble size, and allowing the gas bubbles to re-dissolve, then decompressing slowly enough to avoid further formation or growth of bubbles, or eliminating the inert gases by breathing oxygen under pressure[15]: Ch. 15
therapeutic schedule
Procedure for hyperbaric treatment involving recompression to relieve symptoms, followed by decompression at a rate unlikely to cause a relapse. Use of special breathing gas, particularly oxygen, to increase the rate of elimination of inert gases is common.[16]
A thin but distinct layer in a large body of fluid, in which temperature changes more rapidly with depth than it does in the layers above or below.[17]
Hypothesis that bubble formation during decompression will not occur provided absolute ambient pressure exceeds the total of the partial gas tensions in the tissue for each gas.[18]
A shackle which uses a bolt as the pin, secured with a nut. The nut may be locked with a split pin for greater security. The bolt may rotate in the shackle under load without great risk of unscrewing the pin
The surface interval necessary after diving to reduce tissue gas concentrations to a level where the risk of decompression sickness due to the pressure reduction experienced in normal commercial airliners is acceptable.[15]
A meeting held at the start of each shift or prior to any project critical operation, where the diving supervisor or the diving supervisor’s delegate and shift personnel discuss the forthcoming tasks or jobs and the potential risks and necessary precautions to be taken.[22]
To reconnect a partially filled cylinder and add gas until the pressure is within tolerance of the required charging pressure when corrected for temperature.
A pipe, through which concrete is placed below water level. The top of the tremie is above water and open, and the bottom end is kept below the surface of the poured concrete.
triangular profile
A triangular dive profile is one in which, after a descent at constant rate, and a short bottom time at maximum depth, the diver maintains a constant, slow ascent to the surface or first decompression stop. A plot of depth against elapsed time takes a triangular shape.
A line attached to the top of an open parachute lifting bag and at the other end to an anchor point. Its purpose is to invert and thus empty the bag if it becomes detached from the load.[22]
try-dive
try dive
tryout dive
1. Guided dive using unfamiliar equipment as a marketing technique, in the hope of convincing the diver that the product is worth buying. Some instruction or guidance on the use and characteristics of the product is usual. Similar in concept to test driving a motor vehicle, and similarly, generally offered to qualified operators, except for rebreathers, where one qualifies on a specific type.
2. Also called "Discover Scuba Diving by PADI."[26] A single dive experience under the direct supervision of a recreational instructor offered to uncertified novices in the hope of them deciding to purchase entry level training. Some instruction on the essential skills and risks is generally provided, and the dive is generally conducted in benign conditions.[27] Compare with resort diving.
A seamless transportable compressed gas container, with a water capacity exceeding 150 litres (5.3 cu ft) but not more than 3,000 litres (110 cu ft);[10] Often mounted horizontally in manifolded groups on a trailer or intermodal container frame.[28]
TUP
Transfer under pressure Transfer of personnel between hyperbaric environments, usually between a closed bell and a saturation system, or between a portable recompression chamber and a multi-occupant chamber
The cloudiness or haziness of a fluid caused by individual particles (suspended solids) that may be invisible to the naked eye, similar to smoke in air
turn the dive
Start the return on a dive which has reached the planned turning point in terms of depth, time, gas supply or distance.[6]
twilight zone
Deeper than 60 m in the sea, or the part of a cave or cavern that has dim but discernible ambient light.
Wet diving bell (q.v.) with umbilical supply of gas and other services to the bell, from which they are distributed to the divers umbilicals from a control panel in the bell.
Underwater breathing apparatus: Equipment used to supply breathing gas to an underwater diver. Usually refers to the part of the system carried underwater by the diver.
UDT vest
Underwater Demolition Team vest, An inflatable surface life-jacket worn by underwater demolition teams. Similar in style and a precursor to the horse-collar style buoyancy compensator.[29]
Life support hose and cable bundle connection to a surface supplied diver or diving bell. Comprises gas supply hoses, pneumofathometer, a strength member and communications cable, and may also include gas reclaim hose, hot water hose and hoses for hydraulic or pneumatic power, and electrical and optical cables for ancillary equipment. Underwater television cameras and cabling can also be carried as a component part of the umbilical or can be taped or banded to it on a temporary basis. Also refers to the power, control and instrument cable for a ROV.[22]
Emergency procedure to disconnect the umbilical and connect a replacement in situ during the dive. Usually only used when a delay in recovering the diver or bell is likely.
Mechanism fitted to a closed bell which allows the occupants to sever the bell umbilical from inside the sealed and pressurised bell in the event of an umbilical snag that prevents bell recovery. The device is typically hydraulically operated using a hand pump inside the bell, and can shear the umbilical at or just above the point where it is fastened to the top of the bell.[30]
A subsurface flow of water returning seaward from shore as result of wave action.[31]
underwater blackout syndrome
Also: "hyperventilation-induced blackout"
Loss of consciousness due to hypoxia during a breath-hold submersion preceded by hyperventilation where alternative causes of blackout have been excluded.[32][33]
A fairly substantial natural fibre rope which is deployed from the bottom using a small lift bag to provide the equivalent of a shotline. The lower end is tied off to the bottom, usually on a wreck, and the diver ascends on the line to avoid being swept away from the site by currents. After reaching the surface, the last diver cuts the line and it sinks back down, Natural fibre is used so the line rots away over a few years.[34]
Valve, (usually regulator first stage or demand valve), where the valve mechanism moves against the flow when opening, and the pressure difference over the valve tends to close it.[36]
An oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water.[37]
The widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large veins, large arteries, and smaller arterioles.
Inert gas bubbles formed in the venous circulation.
venting breath
Breathing pattern intended to vent gas from a rebreather loop, usually by exhaling through the nose.[7]
venting tube
Rubber tube closed with a stopper and normally attached to the chest area of an otherwise valveless dry suit, enabling the latter to be completely deflated before entering the water or inflated in the water to make the suit buoyant if required.[39]
An entry technique for relatively high drops, up to and sometimes exceeding 3 m. The feet are overlapped and the legs kept straight. The body and head are kept vertical and the mask and DV held against the face with one or both hands, elbows tucked in. The intention is to hit the water vertically, with the least likelihood of knocking off or damaging vital equipment.[40]: 249
The distance through the water at which an object can just be seen against the background. Often defined as the distance at which a Secchi disc perpendicular to the sight line can first be seen when moving towards it. It can vary depending on direction illumination, and depth.[41]
visual gap
Gap between guidelines which is small enough that each line can be seen from the other.[6]
visual jump
The procedure of crossing a visual gap (q.v.) without the use of a jump line.[6]
visual inspection
Internal and external inspection of a pressure vessel as part of revalidation procedure[10]
The logical procedure in which rebreather electronics compare output from multiple sensors when sensors produce significantly different values, suggesting that one or more are faulty, and choose which signals should be ignored, assuming statistical independence of the sensors, which may not be valid.[7]
Exponential-Linear algorithm used for the 2008 US Navy tables, which assumes exponential ingassing and a combination of linear and exponential outgassing rates.
Recreational scuba diving along the face of a near vertical cliff wall, particularly if the bottom is below the range of the diver's equipment and certification. This requires good buoyancy control.[44]
Ballasted waist belt worn by divers to compensate for excess buoyancy. For scuba and freediving, usually easily removed to establish positive buoyancy in an emergency.
Webbing strap system to support diving weights, usually suspended from the shoulders and fastened around the waist. The harness may carry the weights directly, or they may be carried in pockets on the harness. For scuba diving the weights may be arranged for easy shedding.
The assembly at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment.
A mobile platform used to deploy and recover divers to and from working depth fitted with an air dome and on board emergency gas supply for use as safe haven in emergencies. There may be a main supply umbilical from the surface providing breathing gas to a manifold inside the wet bell and diver excursion umbilicals terminated at the wet bell, or the divers' umbilicals may be direct from the surface.[22]
A close fitting, thermally-insulating, foam neoprene diving suit that allows a limited volume and movement of water inside the suit.
whip
Flexible high pressure gas hose with connector at the free end, used for temporary connections. The other end may be permanently connected to an installation or other equipment, or may also have a temporary connector. Whips are commonly named for their intended use, e.g. filling whip, for filling cylinders, decanting, transfill or transfer whip for decanting between cylinders, oxygen whip for oxygen transfer, blending whip, for decanting gases when blending gas, etc. Accessories may include a flow control valve, bleed valve, pressure gauge, and/or whip check.[48]
whip check
whiplash arrestor
A cable or webbing strap connecting a hose end to the attachment point in addition to the hose end fitting, which restrains the movement of the hose if the connection is broken under pressure. Whip checks connecting two hose ends may also be attached to an anchor point to limit motion further if this is practicable.[49][50]
Whip check device which contains a short section of the whip within a braided tube which reduces wear and point loading on the hose, and constrains motion of the hose end more than a standard whip check in case of disconnection under pressure.[52]
A valve used to connect a regulator or filling whip to a diving cylinder using the CGA 850 "international" connection, mostly used in the US and countries where US diving tourists are economically important.[54]
Cylinder valve body with two outlets and two valve mechanisms which can be independently controlled so that two regulator first stages can be fitted. Similar to H-valve but in Y configuration.
^ abcdefSouth 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.
^Sheldrake1, Sean; Pedersen, Rob; Schulze1, Chad; Donohue, Steven; Humphrey, Alan (2011). Pollock, N.W. (ed.). Use of Tethered Scuba for Scientific Diving(PDF). Diving for Science 2011. Proceedings of the American Academy of Underwater Sciences 30th Symposium. (Report). Dauphin Island, AL: AAUS.{{cite report}}: CS1 maint: numeric names: authors list (link)
^Molland, Anthony F., ed. (2008). "10 - Underwater vehicles". The Maritime Engineering Reference Book: A Guide to Ship Design, Construction and Operation. Butterworth-Heinemann. pp. 728, 730–783. doi:10.1016/B978-0-7506-8987-8.00010-X. ISBN9780750689878.
^Staff, EDTC (16 June 2017). "7 Definitions". Inshore and Offshore Diving Industry Personnel Competence Standards (Draft) (Report). European Diving Technology Committee.
^Britannica, The Editors of Encyclopaedia. "thermocline". Encyclopedia Britannica. Retrieved 16 June 2023.
^LeMessurier, H.; Hills, B.A. (1965). "Decompression Sickness. A thermodynamic approach arising from a study on Torres Strait diving techniques". Hvalradets Skrifter. 48: 54–84.
^"upstream". www.collinsdictionary.com. Retrieved 12 July 2023.
^Harlow, Vance (1999). "1 How a regulator works". Scuba regulator maintenance and repair. Warner, New Hampshire: Airspeed Press. pp. 1–26. ISBN0-9678873-0-5.
^"Upwelling". oceanservice.noaa.gov. National Ocean Service, NOAA. Retrieved 16 June 2023.
^Silbey, Robert J.; Alberty, Robert A.; Bawendi, Moungi G. (2004). Physical Chemistry (4th ed.). Wiley. ISBN978-0471215042.
^British Sub-Aqua Club members (1982). British Sub-Aqua Club Diving Manual (10th ed.). Ellesmere Port, Cheshire: British Sub-Aqua Club. p. 567. ISBN978-0950678610.
^Jablonski, Jarrod (2006). "Details of DIR Equipment Configuration". Doing it Right: The Fundamentals of Better Diving. High Springs, Florida: Global Underwater Explorers. p. 113. ISBN978-0-9713267-0-5.
^Staff. "Whip checks". Houston, Texas: Safety Rig Oilfield and Industrial Safety Products. Retrieved 15 November 2013.
^Staff. "Whip socks". America West Drilling Supply. Archived from the original on 9 October 2019. Retrieved 15 November 2013.
^Rey, Louis, ed. (2012). Arctic Underwater Operations: Medical and Operational Aspects of Diving Activities in Arctic Conditions (illustrated ed.). Springer Science & Business Media. ISBN9789401196550.
^ abcHarlow, Vance (1999). Scuba regulator maintenance and repair. Warner, New Hampshire: Airspeed press. ISBN0-9678873-0-5.
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