Anchor Ball

A black ball-shaped day signal used to indicate that a vessel is at anchor.

It is displayed where it can best be seen so that other mariners can distinguish an anchored vessel from one underway. The signal identifies the vessel’s status; it does not mean that the vessel is “not under command”.

The applicable collision regulations specify which vessels must display the shape and any exceptions. At night or in restricted visibility, prescribed lights are used rather than relying on the day shape alone.