What is a "vessel in sight"?

A "vessel in sight" refers to a situation where one vessel is visually seen and identified by another vessel. This definition is crucial because it establishes the ability of vessels to perceive each other's presence in navigational scenarios, which is essential for maintaining safe maritime operations and ensuring compliance with the COLREGs. When vessels are in sight of each other, they can take the necessary actions to avoid collisions, such as altering course or speed as indicated by the rules.

The other choices do not accurately define "vessel in sight." A vessel in distress pertains to a specific situation involving an emergency, navigational aids refer to equipment used for navigation purposes rather than a specific type of vessel, and a vessel that is anchored does not necessarily imply that it is being visually observed by another vessel. Therefore, the correct understanding is focused on visual identification between vessels, which is key to navigating safely at sea.