When must the lights required by the Rules be shown?

• A. From sunset to sunrise
• B. From sunrise to sunset
• C. Only in fog
• D. Only when anchored

Answer: (A)

Vessel lights are placed to keep others able to see you when natural light is insufficient. The standard requirement is to display the prescribed navigation lights from sunset to sunrise, so a vessel is visible in darkness and its presence and course can be inferred by others. The other options don’t fit because daylight hours typically don’t require the basic navigation lights, lights aren’t limited only to when a vessel is anchored, and while lights are indeed needed in fog or other reduced-visibility conditions, the primary period covered by the rule is nighttime.