Pennsylvania law requires that scuba divers or snorkelers display a flag to mark the diving area. Vessels not engaged in diving operations must remain at least 100 feet away from areas displaying a diver-down flag. Two types of flags are used to indicate diving activity.
A rectangular red flag with a white diagonal stripe must be displayed from a float during diving operations if on state waters.
A blue-and-white International Code Flag A (or Alfa flag) must be displayed from boats during dive operations if the boats are restricted in their ability to maneuver. 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.