Under the U.S. Inland Navigation Rule 20 [c] and 20 [d] anchored vessels more than 23 ft. in length are required to display appropriate lights and shapes where they can best be seen to avoid collisions.
From sunset to sunrise, or in restricted visibility, they must display a white light that is visible in all directions. During the day they must display a black ball day shape, unless anchored in a designated “Special Anchorage Area”.
My friend Salty Clay says that the white anchor light on top of the mast is a common sight in an anchorage. But how many mariners hoist their black ball day shape in anchorages or mooring fields? Not that many.
He also points out that a “Special Anchorage Area” is not just the spot shown on the chart labeled “Anchorage”. It is an area specifically designated by the Secretary of Homeland Security. Not many such special places exist. They can be looked up in The Code of Federal Regulations. Title 33 “Navigation and Navigable Waters.” Part 110. “Anchorage Regulations” at www.access.gpo.gov