What does it mean when a vessel has visible red and green lights?

When a vessel displays visible red and green lights, it is indicating its position and direction as part of navigation rules. Specifically, the red light is displayed on the port (left) side of the vessel, while the green light is displayed on the starboard (right) side. This lighting arrangement is crucial in helping other boaters determine the orientation and movement of the vessel.

The presence of both red and green lights typically signifies that the vessel is under way and has the potential to be approaching. When two vessels are on a collision course, observing these lights allows each captain to assess the situation and take appropriate action to avoid a collision. Therefore, when another vessel sees red and green lights, it understand that it is approaching and should be cautious.

In other contexts, such as a vessel at anchor, only specific lights may be used (usually an anchor light), and a sailboat might be characterized differently based on its rigging or sail configuration rather than solely on its light display. Hence, the interpretation of red and green lights primarily conveys that a vessel under way is navigationally engaged and indicates its approach to others on the water.