What is the purpose of an all-around light on an anchored vessel greater than 100m?

Answer: A — To indicate it is anchored

An all-around light on an anchored vessel greater than 100 meters serves the crucial function of indicating that the vessel is at anchor. According to the COLREGs, an all-around white light must be displayed by vessels that are at anchor to ensure they are visible to other vessels in the area. This enhances safety at sea, as it allows other operators to recognize the anchored status of the vessel, preventing possible collisions or navigational misunderstandings. The presence of this light is especially important in busy maritime areas or during reduced visibility conditions, as it clearly communicates the vessel's position and status to other mariners.