Which of the following is an example of a navigational aid?

A buoy serves as a navigational aid because it is a floating device that can mark channels, warn of hazards, or provide information about navigational routes. Navigational aids are vital in guiding mariners safely through waterways and can assist in understanding water depths, currents, and the locations of land formations or obstructions.

The other devices listed, while valuable in their own right, serve different purposes. A compass is primarily a directional tool that helps determine magnetic north, a sextant is used for measuring angles and determining a vessel’s position by sighting celestial objects, and a fathometer measures water depth. These instruments are essential for navigation, but they do not function as navigational aids in the same way that a buoy does in providing direct assistance or marking courses on the water.