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Glossary - T

Tables These are tables from which you calculate how long and how deep you can safely dive and also details of any decompression stops you have to make on your ascent.
Tachycardia A rapid heartbeat of over 100 beats per minute.
Tank The cylinder that divers carry on their back.
Tank Boot Rubber, vinyl or plastic devices that fit onto the bottom of tanks to allow them to stand upright.
TDI  Technical Diving International
Technical Diving A general term used to describe more advanced diving that requires the use of different gas mixtures.
Test Pressure The pressure to which a cylinder is taken to, during hydrostatic testing.

Thermoclines form when surface water heats from the sun with little or no water motion to mix it with deep water.  Warmer water is lighter than cold water, so temperature layers develop with the warmer water lying on the surface.

Ranges are as little as 1 to 2 Celsius drop or as great as 7 to 8 Celsius drop in temperature with depth.  Thermoclines are most extreme in deep still bodies of water like lakes and quarries.  Most saltwater areas also have Thermoclines although they may not be as extreme because wave currents help mix the different temperature waters.

Thirds Rule A gas management policy of using one third of your gas supply for the initial dive penetration, one third for the exit, and hold back one third as a contingency reserve.
Tidal Volume The quantity of gas that is inhaled and exhaled with each breath.
TP see Test Pressure
Track The path that the boat is intended to follow over the ground.
Transom The flat back section of the boat, where the sides meet the back.
Trim The longitudinal balance of a boat. How the bow and/or stern sits in the water for optimum performance.
Trimix A breathing mixture of three gases, usually Oxygen, Helium and Nitrogen.
True north Is the northern location of the earth's axis of rotation and is the basis for lines of latitude and longitude.
Turn A loop formed around a post, rail, or the line itself.
Twin Set A dual cylinder diving configuration. they may be ganged together or completely separate.










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