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.
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 and 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.
Scuba divers or snorkelers should not place a flag where it will obstruct traffic or create a hazard to navigation on a river, inlet, or navigation channel. Divers and snorkelers must stay within 50 feet of their diver-down flag. (After dusk, the flag must be illuminated so that it can be seen at a distance of 300 feet or more.)
Any vessel used in the diving operation must display from its mast both a divers flag and an Alfa flag visible from all directions. (After dusk, these flags must be illuminated so that they can be seen at a distance of 300 feet or more.)