If a watch stander believes that the relief is not fit for duty, what must he do?

When a watch stander is concerned that the relief is not fit for duty, the responsible course of action is to inform the officer of the watch. This allows for proper assessment of the situation. The officer of the watch has the authority and experience to evaluate the circumstances and take appropriate action, which might include ensuring proper rest, assessing the person's condition, or even temporarily relieving them from duty if necessary.

This protocol is crucial for maintaining safety and operational efficiency aboard the vessel. Immediate action by the watch stander ensures that any potential issues are addressed before they could compromise the watch's effectiveness, maritime safety, or the well-being of the crew. It is vital to rely on the chain of command in situations that could impact the safety of operations, rather than making unilateral decisions that may not consider all factors involved.