What lights must sailboats show when underway at night?

• A. Red and green sidelights and a sternlight
• B. White all-around light
• C. Two white stern lights
• D. One white light only

Answer: (A)

Sailing vessels underway at night must display navigation lights that identify the vessel and show its direction of travel. The required setup is red sidelight on the port (left) side, green sidelight on the starboard (right) side, and a white sternlight at the stern. The red and green sidelights signal to others where the vessel’s front is, while the white sternlight indicates the rear. This combination gives nearby vessels a clear picture of your position and heading, enabling safe decisions to avoid collisions.

Other lighting options don’t provide the same directional information or vessel type: a white all-around light doesn’t indicate that you’re a sailing vessel or show your course; two white stern lights would not convey left-right orientation; a single white light is insufficient to identify both presence and direction.