What does Rule 18 specify regarding vessels not under command?

Rule 18 of the International Regulations for Preventing Collisions at Sea (COLREGs) addresses the responsibilities of vessels not under command and specifies that such vessels are to be given the right of way over all other vessels. This is significant because it acknowledges their inability to maneuver effectively due to their circumstances, which may include mechanical failure or other incapacitating issues.

When a vessel is not under command, it is vital for other mariners to recognize its situation and afford it priority. This rule aims to prevent accidents by ensuring that other vessels take appropriate action to avoid collisions with those that cannot operate normally.

The other options do not accurately capture the essence or requirements of Rule 18. For instance, it does not state that these vessels must always be under sail or that they must keep moving. Assistance might be necessary but is not a condition placed upon them by Rule 18 itself. The rule clearly emphasizes their right of way, which is crucial for maintaining safety on the water.