The acronyms used in diving.


BCD – Buoyancy Control Device

A BCD or Buoyancy Control Device is an air cell that can be inflated or deflated. It is nowadays used by all divers to control buoyancy and help stay comfortably afloat at the surface. Most are in a jacket style of BCD but they can also be what is called wing BCD or even an hybrid of the two. In technical diving it is normally a wing attached to the backplate which can have a double internal bladder for added redundancy.


DCIEM – Defence and Civil Institute of Environmental Medicine

Its was in 1971 in Canada that the DCIEM or Defence and Civil Institute of Environmental Medicine was founded in a joint participation of military and civilian personnel. This lead to the development of dive tables that were more conservative than the US Navy tables.

DIN – Deutsches Institut für Normung

DIN or “Deutsches Institut für Normung”, meaning “German institute for standardisation” is a word used to design tank valve and regulator first stage fittings. The other connection used in scuba diving is the A-Clamp or Yoke.

Divers Alert Network – DAN

Divers Alert Network or DAN is a non-profit agency that collects and analyze information for divers safety. It has branches that sell different diving oriented services and products such as insurance or oxygen providing kits or First Aid and CPR courses.

DPV – Diver Propulsion Vehicule

DPV or Diver Propulsion Vehicule are also called underwater scooters. They are composed of a sealed electric engine with gears that rotates a propeller at various speeds.

DSMB – Delayed Surface Marker Buoy

A DSMB or Delayed Surface Marker Buoy works the same as a SMB but it is inflated and deployed from underwater. It is composed of a surface marker buoy secured by a line on a spool or by a WDS. DSMB allow a diver to be located and spotted from the surface while still being at desired depth. It helps in preventing and avoiding accidents with boats and is considered mandatory in many places.


EAN – Enriched Air Nitrox

EAN or Enriched Air Nitrox is a mixture of gases for which content is the same as air but at different ratios. It has higher concentration of oxygen than the 20.8% found in regular air. EAN is used to reduce nitrogen exposition and saturation into the body. It gives longer bottom times at given depths than regular air.

END – Equivalent Narcotic Depth

END or Equivalent Narcotic Depth is used to express the relative narcotic effect of nitrogen at given depths. Also called rapture of the deep, it impairs divers when they get exposed to a certain pressure. It is different for every diver at different times. The END compares a mixed gas other than air such as nitrox or trimix to what the narcotic effect would if the dive was conducted on air.


fsw – feet of seawater

fsw or feet of seawater is a measurement unit of the imperial system and represent the pressure in 1 foot of seawater or about 15 psi. 33 feet is also roughly 1 atmosphere.


Gauge pressure

The gauge pressure is the pressure shown by a gauge which was calibrated and zeroed using ambient surface pressure at sea level as a reference.


HPNS – High Pressure Neurological Syndrome

HPNS or High Pressure Neurological Syndrome occurs on very deep dive usually past 100m and it affect the central nervous system. Syndromes include tremors, spasms, paralysie. Little is know on the physiological mechanics of HPNS.


ICD – Isobaric Counterdiffusion

ICD or Isobaric Counterdiffusion is a term used to describe when an inert gas is diffusing in the tissues while another inert gas is diffusing out of the tissues. It is not a desirable effect as it leads to increased risk of gas bubbles formation in fast tissues.


LDS – Local Dive Shop

A LDS is a store, shop or dive center that provides products and services related to diving. It can be diving logistics and diving trips, equipment maintenance, rental or sales or education and certification.

LPI – Low Pressure Inflator

The LPI or Low Pressure Inflator allows the BC or BCD to be inflated or deflated. The LPI is fed by its own hose connected to a low pressure port of a regulator first stage. There are only two buttons, one for inflation and the other for deflation.


MOD – Maximum Operating Depth

MOD or Maximum Operating Depth counted in meters is the maximum depth at which a mixture of gas becomes unsuitable for breathing. The high partial pressure of oxygen might lead to seizures and convulsion. It is not used in regular air diving but taught in any enriched air courses or in mixed gases courses in technical diving.

MSW – Metre Sea Water

MSW or Metre Sea Water is the unit used in metric to measure the pressure divers are exposed to. For every meter of sea water the pressure is theoretically 0.1bar and is equal to 3.26336 fsw.


NDL – No Decompression Limit

The NDL or No Decompression Limit is a period of time that a diver can stay according to the depth before decompression is required. The NDL is used in recreational diving to calculate the maximum time a diver can stay and is used when planning dive. Dive computers will calculate this limit at set interval normally in just a few seconds to accommodate changes in depths through the dive.


OC – Open Circuit

Open circuit is the breathing system most commonly used for scuba diving. It is called open circuit because all the gas exhaled by the diver is expelled in the environment. A basic OC breathing apparatus is composed of a cylinder, a regulator first and second stage and a pressure gauge. The other systems are called CCR for closed circuit rebreather or SCR for semi-closed rebreather because they reuse in a loop all or part of the diver exhaled gas.


PSI – Pounds per Square Inch

The PSI or Pounds per Square Inch unit is from the imperial system of measurement and is used to express the value of pressure. Some countries such as the US still use it but most countries in the world use the bar which is the metric unit for pressure measurement.


RNT – Residual Nitrogen Time

The Residual Nitrogen Time or RNT is a way to convert the saturated nitrogen in the body in time to be easier to use with tables.


SI – Surface Interval

The SI or surface interval is the amount of time between 2 dives which is used to calculate the limits in consecutive dives.

SMB – Surface Marker Buoy

A SMB or Surface Marker Buoy is a safety signaling device in the form of an inflatable tube of fabric brightly colored. SMBs are used at the surface to be easily visible and spotted from far away. Some can also be deployed from underwater and are called DSMB.

SPG – Submersible Pressure Gauge

SPG or Submersible Pressure Gauge is a gauge that translate the pressure from the tank to a unit that has measurable properties. Similar to the fuel gauge of a car. They can either be in PSI for imperial system or bar for metric system. They are the same as their regular non-submersible counterpart but sealed to block water from getting into the mechanism preventing corrosion.

SS – Safety Stop

A Safety Stop or SS is a stop or pause that divers do at the end of a recreational dive before surfacing. They are not required in the case of an emergency but are very good practices to help prevent the onset of decompression sicknesses. They are done at 5 meters for a period of 3 minutes.


WOB – work of breathing

The work of breathing or WOB is in simple terms, the effort required by the lungs to breathe. But to be more accurate it refers to the energy expended to inhale and exhale a breathing gas. The WOB is usually expressed as work per unit volume.