BOTH INTERNATIONAL & INLAND Your tug is underway at night and NOT towing. What light(s) should your vessel show aft to other vessels coming up from astern?

Correct Answer: Option A — One white light

Rule 23(a)(iii) requires a power-driven vessel underway to exhibit a stern light. This is a white light showing an unbroken arc of 135 degrees from dead astern. When not towing, a power-driven vessel does not display additional lights aft, such as the yellow towing light.