Which of the following describes a navigational buoy?

A navigational buoy is indeed best described as a floating device that aids in navigation by marking locations. These buoys are strategically placed in waterways to indicate safe passages, hazards, or specific locations of interest for maritime navigation. They serve as essential reference points for mariners, providing visual cues to help with course planning and navigation, especially in areas where charts may not be detailed or when visual landmarks are absent.

Navigational buoys often come in different colors and shapes, each with specific meanings to convey information regarding the navigable channel, safe water locales, or danger zones. The use of such buoys is crucial for ensuring safe and effective navigation, especially in complex or congested waters.

Other options relate to different concepts unrelated to the role of a buoy in navigation. Devices that measure water temperature provide environmental data, a type of vessel used for navigation training is meant for instructional purposes rather than guidance in navigation, and a method of communication between ships encompasses protocols for exchanging information but does not facilitate navigation itself in the way that buoys do.