Any vessel involved in diving operations where persons are scuba diving, skin diving, or snorkeling from a vessel must display a rigid replica of the Alfa flag to mark its diving operation. If operating at night, three all-round lights in a vertical line must be displayed where they can be seen best; the highest and lowest lights must be red with a white light in between. Vessels not engaged in diving operations should remain at a safe distance away from a displayed flag, preferably at least 200 feet away. Some county ordinances may have specific restrictions. Two types of diver-down flags are available.
Two types of flags are used to indicate diving activity.
Divers Flag: A rectangular red flag with a white diagonal stripe (divers flag) may be used to indicate the presence of a submerged diver in the area, but it does not meet the state and federal requirements for display.
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, is required and must be displayed on vessels whenever these vessels are restricted in their ability to maneuver by the diving operation. 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.