Final answer:
After sunset, a vessel at anchor should display an all-round white light that is visible in all directions to signal its presence to other seafarers.
Step-by-step explanation:
After sunset, a vessel at anchor must display an all-round white light that is visible in all directions. These navigation lights help to prevent collisions at night by making the anchored vessel visible to other boats in the area.
The navigation light acts much like the lighthouse that warns ships not to approach too close to dangerous shorelines, by ensuring the vessel's presence is known. While a lighthouse has a beam that covers all directions, an anchored ship must use an anchor light that provides visibility in 360 degrees to signal its position to other seafarers.
It is crucial for the safety on the waters that these regulations are followed. Not only do they prevent accidents, but they also enable a system of communication that is understood by mariners worldwide, similar to the function of streetlights and traffic signals for vehicles on the road.