BOTH INTERNATIONAL & INLAND You see a vessel displaying three lights in a vertical line. The highest and lowest lights are red and the middle light is white. She is also showing a white light at the stern, which is lower than the forward light. It could be a __________.

Correct Answer: Option D — survey vessel

COLREGS Rule 27 governs vessels constrained by their task, such as underwater survey vessels. When underway, they exhibit three all-round lights in a vertical line (red, white, red) alongside sidelights, sternlights, and masthead lights as appropriate.