The Maine Boater Safety Handbook
The Official Boating Handbook of the Maine Department of Natural Resources - Web Version
Table of Contents
The U.S. Coast Guard requires recreational vessels engaged in diving, scuba diving, or snorkeling on federally controlled waters to display the Alfa diver-down flag.
A rectangular red flag with a white diagonal stripe can be attached to a vessel, float, or buoy.
A blue-and-white International Code Flag A (or Alfa flag) must be displayed on vessels on federally controlled waters.