When a vessel on federal waters is taking part in daytime diving operations and has restricted maneuverability, it should display a blue and white Alpha flag which must be at least 20 by 24 inches, and a stiffener is required to keep the flag unfurled if in federal or international waters.
A divers-down flag must be used on state waters. If displayed on a vessel, the flag must be flown from above the vessel's highest point so that the flag's visibility is not obstructed from any point of view. Vessels must not display Alpha flag in state waters.
State law says that when a divers-down flag is displayed there is a person is taking part in diving activities in close proximity of that area. The divers-down flag is red with a white diagonal stripe.
Divers-down symbols displayed from the water must be at least 12 by 12 inches and can be in the form of a flag or a buoy. The buoys must be three or four sided, and have a divers-down symbol displayed on each of the flat sides. A divers-down buoy may not be used or displayed on a vessel.
Divers-down flags displayed from the vessel must be at least 20 inches by 24 inches, and a stiffener is required to keep the flag unfurled.
When taking part in a boating activity in a sector where this flag is displayed, boaters must make a reasonable effort to keep a safe distance of at least 300 feet from divers-down flags or buoys on open waters, and at least 100 feet from flags or buoys on rivers, inlets or navigation channels. Similarly, divers must make a reasonable effort to stay within 300 feet of the divers-down flag or buoy on open waters and within 100 feet of the flag or buoy on rivers, inlets, or navigation channels.
Vessels approaching divers-down flags or buoys closer than 300 feet in open water and 100 feet in rivers, inlets, and navigation channels must slow to idle speed.
When divers are out of the water, a dive flag or buoy must not be displayed.