Scuba divers and snorkelers must display a diver-down flag to mark their diving area. Under no circumstances should a vessel approach within 100 feet of any vessel or object displaying a diver-down flag. Divers should be aware that it is illegal to disturb any underwater archeological site or remove any artifacts without a state-issued permit.
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 with a white diagonal stripe, at least 15 x 15 inches in size, is used if on New York state waters. The flag should be attached to a float.
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.