State law requires that scuba divers and snorkelers display a diver-down flag to mark the diving area. Vessel operators must not operate within 50 feet of a displayed diver-down flag and must reduce speed to “idle speed” when within 200 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 20 x 24 inches when flown from a vessel) with a white diagonal stripe is used to mark the diving area. This flag also must be displayed on vessels 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 state or federally controlled waters. This flag indicates that the vessel is involved in a diving activity.