Scuba divers or snorkelers should display a diver-down flag that marks their diving area.
Vessels must reduce speed to "no wake speed" while within 100 feet of the flag.
Two types of flags are used to indicate diving activity.
Illustrations
Types of Flags
Divers Flag
A rectangular red flag with a white diagonal stripe is used on Idaho state waters.
Alfa Flag
A blue and white International Code Flag A (or Alfa flag) must be displayed on vessels on federally controlled waters.
Skier-Down Flag
Idaho law states that vessels towing person(s) on water skis or other similar devices must carry and use a red or orange skier-down flag, at least 12 x 12 inches in size, whenever the towed person(s) is in the water.