What is the purpose of the identity lights on a pilot vessel?

The identity lights on a pilot vessel serve the specific purpose of identifying the vessel when it is engaged in pilotage duty. These lights are crucial for making it clear to other vessels that the pilot vessel is operating in a capacity to provide pilots to other ships, signaling its role in facilitating safe navigation in confined or busy waters. This identification is essential for ensuring that other mariners recognize the pilot vessel's authority and function, promoting safety and coordination on the water.

In contrast, the other options relate to different functions of lights and signals. Indicating a vessel at anchor would typically involve anchor lights rather than identity lights, which are not intended for that specific purpose. Similarly, signaling that a vessel is underway pertains to navigation lights that demonstrate movement, not identification. Warning other vessels of hazards is related to specific shapes or lights used for marking dangerous areas or obstructions in the water, which differ from the identity lights used for pilot vessels.