Boats must try to stay at least 300 feet away from a vessel displaying a divers' down flag at sea so divers won't be hurt by the boat
. Divers must try to stay within 300 feet of the vessel displaying the flag for safety at sea. Boast must try to stay at least 100 feet from a boat displaying a divers' down flag in rivers, canals and inlets. Divers must try to stay within 100 feet of the boat in rivers, canals and inlets.