Turn Pressure

The tank pressure at which a dive team turns around and heads back, chosen so enough gas remains for the return, ascent, and reserves.

Turn pressure is the gauge reading at which you stop going out and start coming back. It converts gas planning into a single actionable number: when the first diver in the team reaches the agreed pressure, the whole team turns, regardless of how inviting the reef ahead looks. The point is to guarantee enough gas for the return swim, the ascent, the safety stop, and a real reserve on top for the unexpected.

How you set it depends on the dive. On a simple out-and-back from a boat or shore entry, the rule of thirds is a common conservative frame: one third of the gas out, one third back, one third in reserve, with cave and wreck penetration treating thirds as an absolute minimum. Rock bottom planning works the other way, computing the gas two divers need to ascend together from maximum depth and reserving that amount as untouchable. Guided drift dives may instead use a simple reserve like surfacing with 50 bar.

Whatever the method, turn pressure is agreed during the dive plan and briefing, checked against the smallest tank and the highest consumer in the team, and communicated underwater with pressure hand signals. It also deserves a moment of honesty during planning: if the reserve math only works with optimistic consumption numbers, the plan needs shortening, not the reserve. The gauge does not negotiate, and neither should the turn.