What is the required waiting time for a crew member to perform duties after deep water diving?

The required waiting time for a crew member to perform duties after deep water diving is 12 hours. This guideline is established to minimize the risk of decompression sickness, or "the bends," that may occur when a diver ascends too quickly or resumes activities that could exacerbate the condition.

When a diver returns to the surface after deep diving, dissolved nitrogen from the breathing gas can come out of solution and form bubbles in the bloodstream and tissues, potentially leading to severe medical issues. By observing a waiting period of 12 hours before engaging in flight operations or other duties, crew members significantly reduce the chances of developing these complications.

The other options suggest longer waiting times, which may not be necessary for all scenarios of deep diving, especially when considering the specific guidelines set forth by aviation authorities regarding dive operations and return to duties. Therefore, 12 hours is seen as the standard and safe period of waiting for crew members.