When should a vessel take action to avoid a collision according to COLREGs?

A vessel should take action to avoid a collision as soon as it becomes apparent that the danger of collision exists. This principle is grounded in the COLREGs, specifically Rule 2, which emphasizes the need for a vessel to take appropriate action to avoid collision, regardless of the circumstances. By taking action promptly upon recognizing the risk, the vessel can effectively prevent an incident.

Considering the other options, taking action only during bad weather overlooks the necessity of vigilance in all conditions, as dangers can arise at any time. Similarly, limiting action to when another vessel signals is inappropriate since a vessel must be proactive in assessing its own navigation situation without waiting for external prompts. Lastly, stating that action should only be taken in a crowded harbor neglects the fact that a danger of collision can occur in any maritime environment, including open waters. Therefore, the best practice is to anticipate potential risks and act promptly before a collision occurs.