The Extended Range and Trimix Manual (Metric) is the text-book literary assistant to the TDI Extended Range and Trimix certification course.

Extended Range diving is exploring the limits of up to 180 FSW (55MSW) for air as a bottom mix and up to 200 FSW (60 MSW) for basic trimix. Within this range, the diver can explore many additional sights that are beyond the standard recreational Open Water limit of 130 FSW (40 MSW).

With the Extended Range course behind them, a diver will be properly equipped to evaluate and plan dives where some of the less frequently visited wrecks lie, some potentially rare fish can be sighted, as well as interesting geological features.