Scuba divers or snorkelers may not dive within 50 feet of a vessel engaged in fishing, and they should display a diver-down flag that marks their diving area. Vessels must remain at least 50 feet away from the flag. If they have to approach the diving area, operators must have permission from the person who placed the flag or the boat displaying the flag. Outside of 50 feet, vessel operators must operate at idle speed out to a distance of 150 feet. Patrol or rescue craft are exempt from such requirements, especially in an emergency.
Two types of flags are used to indicate diving activity.
Divers Flag:A rectangular red flag, at least 15 inches by 15 inches, with a white diagonal stripe is used if on South Carolina 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 a vessel on federally controlled or international 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.