What is a lightship?

A lightship is defined as a vessel equipped with a light and serves as a navigational aid for maritime traffic. Unlike fixed lighthouses that are stationary, lightships are mobile and can be positioned at specific locations where constructing a lighthouse is impractical. These vessels are often anchored at strategic points to mark hazardous areas, safe passage routes, or important landmarks in navigation.

The key function of a lightship is visibility; it not only has a prominent light that can be seen from great distances but may also feature sound signals, radar reflectors, and other navigational aids to assist mariners. Their role is crucial in ensuring safe navigation in coastal and offshore waters, especially in areas with difficult geography or where shallow depths preclude the construction of a permanent structure.

In contrast, the other options describe vessels serving entirely different purposes: military operations, cargo transport, and passenger ferry services do not fit the specific definition of a lightship and its primary function in navigation.