What does "Not under command" indicate?

The term "Not under command" specifically refers to a situation where a vessel is unable to maneuver as required by the navigation rules. This typically occurs due to the loss of both engine power and steering capability, preventing the vessel from responding to navigational commands.

When a vessel is classified as "not under command," it signals to other mariners that it cannot safely navigate and must be given the right of way in situations where it cannot act to avoid collisions. This distinction is crucial for maintaining safety on the water, as it informs other vessels of the potential danger and the need to exercise caution.

The other options describe different scenarios, but do not accurately define "not under command." For instance, being anchored is a state of rest and does not imply any loss of maneuverability. Similarly, while a sinking vessel may indeed be in a critical situation, it is not synonymous with the term "not under command." A vessel in distress can encompass a wider range of situations, yet does not specifically indicate the loss of maneuverability characteristic of being "not under command."