In addition to sidelights, what additional light should a vessel being towed show?

When a vessel is being towed, it must display both sidelights and a stern light in order to adequately signal its position and movement to other vessels. The sidelights, which are red and green, indicate the sides of the vessel, while the stern light is white and shows the rear of the vessel. This combination is essential for safe navigation, particularly at night or during conditions of reduced visibility. The use of a stern light helps ensure that other vessels can determine the direction in which the towed vessel is moving, as well as its overall length and configuration.

The other answer options do not align with the requirements for lighting on a towed vessel. A bow light is typically not required for a vessel that is being towed, as the sidelights cover that aspect when the vessel is observed from the front. Flashing lights and beacon lights are usually employed for specific types of vessels, such as those engaged in fishing or for emergency situations, but are not standard requirements for a vessel being towed. Therefore, the correct requirement is for the towed vessel to show a stern light in addition to its sidelights.