Federal and state law requires that scuba divers and snorkelers display a diver-down flag to mark the diving area. Alabama law requires that vessel operators stay at least 100 feet from a displayed 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 is used to indicate the presence of a submerged diver in the area. Alabama law requires that divers prominently display this flag and stay within a 50-foot radius of the flag.
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.