What does 'Towing light' refer to?

'Towing light' refers specifically to a light displayed by a vessel that is engaged in towing another vessel. According to the International Regulations for Preventing Collisions at Sea (COLREGs), the towing light is typically a yellow light that indicates to other vessels that the towing vessel is longer than usual due to the presence of a tow, which might affect navigation and maneuverability. This light is critical for ensuring that other vessels are aware of the towing operation, as it allows for better situational awareness and helps prevent potential collisions.

The correct understanding of a towing light is essential for maintaining safety at sea, and it differentiates the towing vessel's operational status from other types of vessels. In contrast, the other options refer to different navigational indicators that serve separate purposes, such as indicating a vessel underway or at anchor, but they do not specifically denote the special status of a vessel that is towing.