Which vessel type is NOT required to show masthead lights?

The correct answer is that towed vessels when stationary are not required to show masthead lights because they are not considered to be underway. According to the COLREGs (International Regulations for Preventing Collisions at Sea), a vessel is defined as "underway" when it is not anchored, moored, or aground. When a towed vessel is stationary, the rules regarding the display of lights change. It is sufficient for stationary vessels to display anchor lights.

In contrast, power-driven vessels and non-power driven vessels that are underway must display masthead lights to ensure proper visibility and to prevent collisions. This is essential for the safe navigation and recognition of vessels in various conditions, especially at night or during limited visibility. Additionally, vessels that are underway must display the appropriate lights according to their type and activities, as specified by the COLREGs.