The duration budget
Time under water gets planned the way depth does.
Because recovery durations have their own distribution, underwater time becomes a budgetable quantity rather than an unpleasant surprise. A drawdown sitting comfortably inside its depth band but far past its duration percentile is flagged while still shallow. Slow bleeds evade depth alarms by design, since they never spike, and the duration read is the only instrument that catches a leak which never produces a bad day.

