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Glossary - B

Backing If a wind is Backing it is shifting in an anti-clockwise direction, for example, shifting over time from the West to South West. The opposite of this is veering.
Backup The concept of carrying fully functional backup systems to replace primaries in the event of failure.
Bailout A small cylinder, (usually 3-4 litre) commonly used as an emergency breathing system in commercial diving, also known as a Pony bottle.
Ballast Any solid or liquid weight carried in a vessel to increase the draught, to improve trim or to regulate stability.
Bathyscape A strong, hollow vessel designed for underwater exploration with its own system of buoyancy control so that an attached cable is not needed to control descent and ascent
Bar A measure of pressure, 1 bar = atmospheric pressure or about 15lbs per square inch.
Barodontalgia Pain & discomfort caused by the volume and pressure changes in teeth 
Barotrauma Injuries resulting from the inability of expanding gasses to exit the body. For example, ear drum rupture,  lung over expansion injury, pneumothorax, squeeze, sinusitis.
BCD Buoyancy Control Device, sometimes called a stab jacket (stability). An inflatable jacket worn by divers. This provides buoyancy and holds the diving cylinder.
Beacon Any object that serves as a signal or indication for guidance or warning. A fixed (non-floating) aid to navigation.
Beam The widest part of a vessel measured between the gunwales.
Bearing Horizontal direction of an object from an observer, expressed as an angle from a reference direction (e.g. compass bearing, true bearing, relative bearing).
Bear Off Steer away from the wind, shore or any object.
Bend A knot that joins two lines of unequal thickness.
Bends See: DCS
Bioluminescence Simply light produced by a chemical reaction which originates in an organism.
Bight The part of the rope between the end and the standing part. A loop formed by folding the rope back on itself.
Bitter End The free end of a line or rope.
Bollard Stout post on wharf or pier for securing mooring lines.
Booties The boots that are worn with fins. Also used to describe the thick socks worn under the drysuit.
Bottom Mix A breathing mixture used at the deepest portion of a dive.
Bottom Time Often calculated from the start of the diver's descent until the beginning of his ascent, or to the safety stop or first decompression stop. Note: This measurement varies widely from organisation to organisation, and some divers do not calculate the safety stop into their total bottom time.
Bow The front end of a vessel.
Bowline A knot used to form a temporary loop in the end of a line. See Knots.
Boyles Law At a constant temperature, the volume of a given mass of gas is inversely proportional to the absolute pressure; if the pressure
goes up the volume goes down and vice versa.
Bradycardia A heartbeat of less than 60 beats per minute.
Broach The turning of a vessel broadside (90°) to the wind or waves, subjecting it to possible capsize (to turn over).
BSAC British Sub Aqua Club.
BSOUP  British Society Of Underwater Photographers
BT Bottom Time
Buddy Your diving partner. BSAC strongly recommend that divers always dive in pairs for safety.
Buddy Breathing An emergency out-of-air procedure where two divers share one second stage regulator while ascending to the surface.
Buddy Check A pre-dive check where two divers familiarise themselves and check each others equipment prior to a dive.
Bulkhead A vertical partition or wall.
Buoy Anchored floating object, marking a channel, hidden dangers, etc.
Buoyancy The upward force equal to the weight of water which is being displaced by an immersed object.
Burst Disk a part of a tank valve that prevents the pressure in a scuba tank from exceeding maximum operating pressure by bursting and venting the tank.










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Page last updated on October 16, 2007
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