What does a vessel greater than 100 meters need to display when anchored?

A vessel greater than 100 meters at anchor is required to display certain lights to ensure visibility to other vessels, as per the COLREGs. When at anchor, this type of vessel must show the anchor lights which typically includes an all-around white light.

While all deck lights may enhance visibility, the critical requirement is the all-around white light. The use of numerous deck lights helps in making the vessel more conspicuous, but it is primarily the all-around white light that meets the minimum legal requirement for vessels at anchor of this size.

Therefore, while having all deck lights on does improve visibility and can serve to inform other vessels of the anchored position, the specific requirement is the display of the relevant anchor light. This ensures safety and operational integrity in maritime navigation.