State law requires that scuba divers or snorkelers display the diver-down flag to mark the diving area. Vessel operators must not operate within 100 feet of a displayed diver-down flag. Divers must surface within 50 feet of the flag.
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.
Two types of flags are used to indicate diving activity.
Divers Flag: A rectangular red flag, at least 12 x 12 inches, with a white diagonal stripe that at least 3 inches in width is used on state waters.
Alfa Flag: A blue-and-white International Code Flag A (or 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.