What may a vessel of less than 12m in length exhibit instead of the lights prescribed for a power-driven vessel underway?

A vessel of less than 12 meters in length may exhibit one all-round white light instead of the lights prescribed for a power-driven vessel underway. According to the COLREGs (International Regulations for Preventing Collisions at Sea), vessels under 12 meters are permitted to display this simpler lighting arrangement for ease of visibility and to reduce the complexity associated with smaller vessels.

This all-round white light can be displayed in lieu of the required masthead light and sidelights that larger vessels must show when underway. The goal is to ensure smaller vessels maintain visibility without the need for elaborate lighting setups that may not be practical or necessary for their size, thus promoting safety on the water.

While an all-round flashing yellow light is typically used for hovercraft or special vessels engaged in specific operations, it is not appropriate for general vessel use as a substitute for the prescribed navigation lights. The other options, such as two masthead lights or a single red and green sidelight, do not align with the regulations regarding vessels under 12 meters, as these vessels are not required to have such setups.