What lights are shown by a vessel underway and engaged on pilotage duty?

A vessel underway and engaged on pilotage duty displays specific lights to indicate its status and ensure safe navigation. The correct answer, which indicates that the vessel shows two all-round lights in a vertical line (one upper white and one lower red), along with sidelights and a sternlight, aligns with the requirements of the COLREGs for vessels engaged in pilotage.

The upper white light signifies that the vessel is under way, while the lower red light indicates that it is engaged in pilotage duties. This combination enhances visibility and communicates to other vessels that the vessel is acting in the capacity of a pilot. Additionally, the requirement for sidelights and a sternlight ensures that the vessel is properly illuminated from all angles, contributing to overall safety in navigation.

In summary, the presence of the two all-round lights, along with sidelights and sternlight, clearly communicates the dual function of the vessel: it is both under way and performing pilotage duties. This is essential for alerting other vessels to its activities, enhancing safety and situational awareness on the water.