What is expected of a vessel that is “not under command”?

A vessel that is classified as "not under command" is one that cannot maneuver as required by the Navigation Rules due to exceptional circumstances, such as mechanical failure or other emergencies. According to the International Regulations for Preventing Collisions at Sea (COLREGs), such vessels have specific requirements to ensure they are visible to other vessels and to help prevent collisions.

Displaying the correct lights is vital for a vessel "not under command" as it communicates its status to other mariners. This typically involves showing two all-round red lights in a vertical line. By displaying these lights, the vessel indicates that it is unable to take any action to avoid a collision, thus alerting nearby vessels to exercise caution. The requirement to indicate its condition is crucial for maritime safety, ensuring that other vessels can correctly assess the situation and navigate accordingly.

The other options presented do not accurately reflect the regulations or expectations for a vessel in this situation. While it is important for vessels to follow the rules, being "not under command" does not exempt a vessel from signaling its status and responsibilities on the water.