How should remaining air time be allocated if a diver is at 40 fsw?

The allocation of remaining air time during a dive, particularly at a depth of 40 feet of seawater (fsw), needs careful planning to ensure safety and minimize the risk of decompression sickness. The correct choice involves a distribution that allows for a significant amount of time at a shallower depth, which is essential for safe ascent and ventilation of residual nitrogen in the body's tissues.

Allocating 10% of remaining air time to 40 fsw is prudent since this depth is where the diver currently is, and they will need to make adjustments before proceeding. The allocation of 20% to a 30 fsw stop provides a necessary decompression point before the final ascent. The most substantial portion of the time, 70%, is allocated to a stop at 20 fsw, where the diver can safely finalize their decompression. This increased time at 20 fsw allows for thorough nitrogen off-gassing, significantly reducing the risk of complications.

The structure of time management in this answer emphasizes the importance of gradually reducing pressure and allowing adequate time to off-gas nitrogen, especially when diving at depths where shorter ascent times might not provide enough safety margin against decompression sickness. The other options either don't allocate enough time at critical decompression stops or