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Scuba Diving Glossary
BACKSCATTER: Light from a flash or strobe reflecting back from particles in the lens' field of view causing specks of light to appear in the photo. Backscatter can be a common problem in underwater photography because particulate matter can be very dense and include plankton which would otherwise be near transparent. Backscatter can be reduced and in many cases removed altogether using various photographic techniques.
BAR: A measure of pressure (not commonly used in the North American Scuba Market). 1 bar = atmospheric pressure or about 14.7lbs per square inch (PSI).
BAROMETRIC PRESSURE: Same as atmospheric pressure with the exception that it varies with the weather.
BAROTRAUMA: Any disease or injury due to unequal pressures between a space inside the body and the ambient pressure, or between two spaces within the body; examples include arterial gas embolism and pneumothorax.
BODY SUIT: A garment that provides full length abrasion protection.
BOTTOM TIME: The time between descending below the surface to the beginning of ascent.
BOYLE'S LAW: At a constant temperature, the pressure of a gas is inversely proportional to its volume.
BREATH-HOLD DIVING: Diving without life support apparatus, while holding one's breath.
BUBBLE: A collection of air or gas surrounded by a permeable membrane through which gases can enter or exit.
BUOYANCY: The upward force exerted on an object in liquid, whether the object sinks or floats. Objects that float are positively buoyant, those that sink are negatively buoyant, and those that stay where placed are neutrally buoyant.
BUOYANCY COMPENSATOR DEVICE (BCD): An inflatable vest worn by the diver that can be automatically or orally inflated to help control buoyancy; abbreviated BC or BCD (Buoyancy Control Device).
BUOYANCY CONTROL: The practice of controlling one's buoyancy.
BURST DISK: Thin copper disk held in place with a vented plug. Designed to rupture if tank pressure is greatly exceeded.