What is the required action for a vessel under oars during nighttime?

For a vessel operating under oars at night, it is required to display an all-round white light. This lighting requirement is necessary to ensure that the vessel is visible to other mariners, signaling its presence effectively, particularly in low visibility conditions that nighttime presents.

The all-round white light provides a 360-degree field of visibility, which is essential for safety on the water. It allows other vessels to easily identify the position and orientation of the oared vessel, reducing the risk of collisions. The visibility of an all-round white light is critical in preventing accidents, as other boats can see it from any angle.

In contrast, the other options do not align with the regulation for vessels under oars at nighttime. Sidelights and a sternlight are designated for power-driven vessels, while showing no lights or a single red light would not adequately signify the presence of a vessel under oars, thus compromising safety.