State law requires that scuba divers or snorkelers display a diver-down flag to mark the diving area. Divers and snorkelers must stay within 75 feet of a diver-down flag at all times. Vessel operators must stay at least 150 feet away from a displayed diver-down flag. If there are circumstances that prevent the vessel from staying 150 feet way from the diver-down flag, the operator must throttle down to headway speed. Two types of flags are used to indicate diving activity.
Two types of flags are used to indicate diving activity.
Divers Flag: The divers flag is a rectangular red flag with a white diagonal stripe used to indicate when diving activities are in progress on New Hampshire state waters
Alfa Flag:On federal waters, you also may see a blue and white International Code Flag A (or Alfa flag) displayed on a vessel engaged in diving operations.
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.