Glossary of SCUBA Diving - R

R

rapture of the deep

see nitrogen narcosis

rash vest

Also known as rash guard, or rashie, A shirt made of spandex and nylon or polyester to protect against rashes caused by abrasion. These shirts can be worn by themselves, in tropical water, or under a wetsuit.

Rat hat

Ratcliffe diving helmet, Designed by Bob Ratcliffe, later produced by Oceaneering International. No longer in production..

ratio decompression

also ratio deco

A technique for calculating decompression schedules for scuba divers engaged in deep diving without using dive tables, decompression software or a dive computer.

rebreather

Breathing apparatus which recycles most of the exhaled gas, removing carbon dioxide and topping up oxygen before the gas is breathed again.

reciprocating compressor

Compressor in which the volume of the compression chamber/s is cyclically changed by reversing linear motion. E.g.: a piston moving back and forth in a cylinder.

reclaim helmet

See also: Saturation diving

Diving helmet with a reclaim gas regulator allowing exhaled gas to be safely returned to the surface through an additional hose on the umbilical.

reclaim system

See also: Saturation diving

System for recovering helium based breathing gas used by divers and recycling it.

recompression chamber

A hyperbaric chamber used to treat divers suffering from certain diving disorders such as decompression sickness.

recreational diving

Recreational diving or sport diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. In some diving circles, the term "recreational diving" is used in contradistinction to "technical diving", a more demanding aspect of the sport which requires greater levels of training, experience and equipment.

Recreational Dive Planner

also RDP

A no-stop decompression table developed by DSAT.

red tide

see algal bloom

regulator

1. A mechanism for controlling the output pressure of a high pressure gas supply.

2. As 1, with a demand valve (q.v.) incorporated which provides the diver with breathing gas at ambient pressure.

regulator freeze

Further information: Ice diving#Regulator freezing

Locking of the regulator mechanism caused by freezing of the water due to expansion cooling of the regulated air. Often causes the mechanism to lock open, causing free flow and further cooling.

reject criteria

Features, states or conditions which are not acceptable.

repetitive dives

Further information: Decompression (diving)#Repetitive dives

Any dive which is done while the tissues retain residual inert gas from a previous dive.

Repex

Method of estimating tolerable repetitive exposure to high partial pressure oxygen..

reserve gas

Further information: Scuba gas planning#Reserve pressure

Gas which is not intended to be used during the dive, and is reserved for contingencies.

reserve valve

Cylinder valve with a lever operated bypass valve to release the gas below reserve pressure

residual gas

Gas remaining in a cylinder from the previous fill.

residual nitrogen

See also: Decompression (diving)#Residual nitrigen time

Nitrogen in excess of normal atmospheric saturation remaining in the diver's tissues after a dive.

residual nitrogen time

also RNT See also: Decompression (diving)#Residual nitrigen time

Time penalty in a repetitive dive equivalent to time at depth which would produce the residual nitrogen in the diver at the start of the dive.

residual pressure

Pressure of the gas remaining in a cylinder from the previous fill.

respiratory quotient

The ratio of carbon dioxide produced as a metabolic product to the oxygen consumed.

restriction

Section of a cave which is difficult to pass through due to lack of space.

RGBM

also reduced gradient bubble model

A bubble model decompression algorithm developed by Bruce Wienke.

rip current

A strong localised flow of water to seaward from near the shore, typically through the surf line

riser

A conduit that provides a temporary extension of a subsea oil well to a surface drilling facility

RMV

Respiratory minute volume: (or minute ventilation) The volume of gas inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs in one minute.

RNPL

Royal Navy Physiological Laboratory

RNT

see residual nitrogen time

ROV

Remotely operated underwater vehicle.

roughneck

Member of the drilling crew who works under the direction of the driller to make or break connections as drillpipe is tripped in or out of the hole.

roustabout

Any unskilled manual laborer on the rigsite.

run time

Time elapsed since the start of a dive.

run time schedule

Decompression schedule and dive plan based on elapsed time from the start of the dive, All waypoints and events are specified in terms of elapsed time with start of descent at zero.