Persons scuba diving, skin diving, snorkeling, or underwater spearfishing must display a diver-down flag to warn other boaters.
- Unless there is an emergency, a diver may not surface more than 25 feet from the flag.
- It is unlawful to display a diver-down flag when not diving.
- No person may operate a vessel within 50 feet of a diver-down flag.
Two types of flags are used to indicate diving activity.
A rigid rectangular red flag, at least 14 x 16 inches, with a white diagonal stripe that is one-fifth the width of the flag must be mounted on a float or buoy.
A rigid replica of the International Code Flag A (or blue and white Alfa flag), at least 3.3 feet (one meter) high and visible from all directions, must be displayed on vessels on federally controlled waters. This flag indicates that the vessel is involved in a diving activity.
Scuba divers and snorkelers should not place a flag in an area already occupied by other boaters or where their diving operation will impede the normal flow of waterway traffic. Divers also should follow all of the water safety rules themselves.