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Glossary - R


Radar An acronym for radio range and detecting. A radio detection device that uses pulses of microwave-length energy to provide range, azimuth, and/or elevation data of objects.
Rebreather A device that reuses air by scrubbing or removing the carbon dioxide from it. There are usually no or very little bubbles emitted.
Recompression The accepted treatment for decompression sickness, CAGE and Lung over expansion injuries. Treatment is instituted by "returning" the diver to a higher pressure environment in a Hyperbaric chamber.
Recompression Chamber Hyperbaric chamber. Used to recompress divers with decompression illnesses. They are slowly brought back to normal pressure allowing nitrogen (or other gases) to be exhaled harmlessly.
Redundancy The concept of carrying fully functional backup systems to replace primaries in the event of failure.
Reg Regulator, the device that you breathe from. Sometimes referred to as the second stage.
Repetitive Dive Any dive following a previous dive within a particular time frame. This will vary according to the particular decompression model being used.
Residual Nitrogen The residual nitrogen (above normoxic levels) left in the body as a result of a previous dive.
Residual Volume The quantity of air remaining in the lungs after a forceful exhalation.
Respiration The voluntary or involuntary movement of gas into and out of the lungs and the associated metabolic process of oxygen and carbon-dioxide transfer.
Rhumb lines Curved lines on the surface of the earth that cut all meridians of longitude at the same angle.
RIB Rigid Inflatable Boat, commonly used by divers.
Rip Tide

A Rip tide is a roughening of the water, or at least a break in the surface pattern caused by the meeting of opposing tidal streams.

RMV Respiratory Minute Volume. The amount of air that is consumed in one minute on the surface. This is expressed in cubic feet per minute.
RNLI Royal National Lifeboat Institute.
ROV Remotely Operated Vehicle, often carrying video cameras.
Rule of thirds A rule used primarily by cave and wreck divers that basically states that after having consumed 1/3 of your gas supply you should begin your exit from the cave/wreck. The remaining 2/3 of the gas supply is left for the exit, ascent and any emergency that may arise.
Running Lights Lights required to be shown on boats underway between sundown and sunup.
RYA Royal Yachting Association









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