Under what condition can a lookout leave his station?

A lookout is responsible for maintaining constant vigilance and ensuring the safety of the vessel and its passengers by watching for potential hazards or other vessels. The correct condition under which a lookout can leave their station is when they are properly relieved by another qualified person. This ensures that there is always someone monitoring the surroundings and maintaining safety on board. If a lookout were to leave without being properly relieved, it could create a lapse in supervision, increasing the risk of accidents or collisions.

In contrast, leaving at the end of a watch or 15 minutes before the end of the watch does not ensure continuous coverage, as it could leave the vessel unmonitored during critical times. Additionally, being able to leave at any time disregards the essential duty of vigilance that a lookout must uphold. The requirement to be properly relieved promotes a safety culture on the water, reinforcing the importance of constant alertness in maintaining maritime safety.