What kind of light is shown by a vessel at anchor at night?

A vessel at anchor is required to display an all-round white light at night. This lighting requirement is specifically mandated by the Navigation Rules to ensure that other vessels can see the anchored vessel from any direction, thus promoting safety on the water. The all-round white light must be visible from a distance of at least two miles in all directions and is typically positioned at a location that ensures it is unobstructed, enhancing visibility.

An all-round white light serves the critical function of alerting other boats that the anchored vessel is stationary, allowing for safe navigation in its vicinity. In contrast to other types of lights that indicate movement or specific maneuvers, the all-round white light signifies that the vessel is not in motion and is anchored. This is essential for preventing collisions and ensuring that navigating vessels can adjust their courses accordingly.

The other light options mentioned do not fulfill the requirements for a vessel at anchor according to the navigation rules, making them inappropriate in this context.