Which one of the following is NOT one of the three types of bearings?

The reason that fathom is the correct response lies in the definitions of the other terms related to navigation. True bearing, magnetic bearing, and relative bearing are all terms that describe methods of determining the direction to a particular point or object on the earth's surface, which are essential for navigation at sea.

• True bearing is the angle measured in degrees from true north to the object, providing an absolute direction regardless of magnetic influences.
• Magnetic bearing involves measuring the angle from magnetic north, which can vary depending on the observer's location and the local magnetic declination.
• Relative bearing is the angle measured from the ship's current heading to the target, making it a useful reference for navigating relative to the vessel's direction.

In contrast, a fathom is a unit of measurement used to express the depth of water, not a type of bearing. It specifically equals six feet and is primarily utilized in maritime contexts to ensure safe navigation and anchoring. Therefore, fathom does not belong to the category of bearings used for navigation, making it the correct choice in this context.