Under what circumstances should vessels display navigation lights?

Vessels are required to display navigation lights at all times when they are underway, which means they are not only in operation but also actively navigating through the waters. This guideline ensures that vessels are visible to one another, reducing the risk of collisions both during the day and at night. Navigation lights provide critical information about a vessel's position, heading, and status, thereby enhancing safety on the water.

Displaying lights only in specific conditions, such as daylight or nighttime, would compromise safety and could lead to navigational hazards. It is essential for vessels to maintain proper visibility regardless of the time of day or whether they are in port or navigating, which is captured by the requirement to have lights on whenever the vessel is in operation.