Scuba divers or snorkelers must display a diver-down flag to mark their diving area. Bubbles also may indicate that a diver is below. Vessels must maintain a distance of at least 25 yards from any displayed diver-down flag. The two types of diver-down flags are:
Scuba divers or snorkelers should not place the flag where it will obstruct navigation, nor should they display a diver-down flag when they are not engaged in diving.