When must a pilot boat exhibit sidelights and a stern light?

The requirement for a pilot boat to exhibit sidelights and a stern light is specifically tied to when it is underway. According to the COLREGs (International Regulations for Preventing Collisions at Sea), any vessel that is not anchored, moored, or aground must display appropriate navigation lights to ensure its visibility and the safety of other vessels.

While a pilot boat is engaged in pilotage duty, it is considered to be underway, meaning it is in operation and thus required to show the correct lights. The sidelights indicate the orientation of the vessel—green on the starboard side and red on the port side—while the stern light serves to show its presence from behind.

In contrast, when a pilot boat is anchored or not in motion, it would display different lights or none, depending on specific conditions, thus eliminating options related to those scenarios. During the day, pilot boats may not be required to show lights if they are clearly visible, but at nighttime or in poor visibility, the lights are vital for safe navigation.