What light arrangement must sailboats show when underway at night?

• A. Red and green sidelights and a stern light
• B. A towing light above the stern light
• C. One all-round white light
• D. A blue light

Answer: (A)

The main idea is that you must be visible to other vessels with the standard navigation lights that indicate both movement and direction. For a sailboat underway at night, that means showing red and green sidelights plus a white stern light. The red sidelight is on the port (left) side and the green sidelight on the starboard (right) side, and a white light at the stern shows you’re moving forward. This combination lets other vessels know which way you’re headed and that you’re under way.

The other options don’t fit because a towing light above the stern is only used when you’re actually towing another vessel; a single all-round white light isn’t the required configuration for a sailing vessel under way; and a blue light isn’t part of standard sailing navigation lights.