What type of light is required to be 360 degrees?

A 360-degree visibility light is referred to as an all-around light. This type of light serves the purpose of providing visibility to vessels from all directions, making it essential for safety in navigation. An all-around light is typically white and must be displayed by vessels to indicate their presence, especially when they are not under power or are engaged in specific operations at night or during reduced visibility conditions.

In contrast, side lights and stern lights have specific functions that do not require them to have 360-degree visibility. Side lights are restricted to a certain arc, usually covering the forward sides of the vessel, while the stern light is directed towards the rear. The masthead light, though it may have a more extensive range than side or stern lights, is also not designed to provide full 360-degree visibility as mandated for an all-around light. Thus, the all-around light is the correct answer, as it is specifically required to be visible from all angles, ensuring that a vessel can be seen and identified by others regardless of their approach angle.