What are the characteristics of a "not under command" vessel?

A vessel classified as "not under command" is one that is unable to optimize its maneuverability due to exceptional circumstances, which could include mechanical failure, grounding, or other unforeseen situations that prevent it from safely navigating. In maritime law, this designation is crucial because it signals to other vessels that they should take extra precautions when operating near this vessel. The term implies that the vessel is facing situations that make it incapable of following standard navigation rules, hence it must be treated with specific consideration by nearby vessels.

Other options do not represent the conditions that define a "not under command" status. For instance, reduced speed due to mechanical issues does not necessarily mean the vessel cannot maneuver; it may still be operational, albeit at a slower pace. A vessel that is docked is securely positioned and confirmed to be able to maneuver, just not necessary; this does not reflect the "not under command" situation. Lastly, a crew changeover occurs when a vessel is operational and capable of navigating, but perhaps temporarily stationary, which again does not fit the definition of being unable to command the vessel's movement.