What is the purpose of navigation lights on a boat?

The purpose of navigation lights on a boat is to indicate the boat's position and direction to other vessels at night. These lights are crucial for safety and communication on the water, especially when visibility is low. The specific colors and placements of navigation lights are standardized internationally, allowing other boaters to determine the type of vessel, its orientation, and its direction of travel. For instance, a red light on the port side and a green light on the starboard side convey critical information about the approaching boat's heading.

Other options provided do not align with the primary function of navigation lights. While illuminating the interior of the boat might be useful for visibility onboard, it does not play a role in signaling to others. Attracting fish is an entirely different activity involving other equipment rather than navigation lights, and warning vessels of shallow waters generally relies on buoys or markers rather than lights.