| 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 |
