The Maritime flag for diving is the “diver down- keep clear” or better known as the A or Alpha flag. This is a white and blue burgee flag. There is, however, a special scuba flag. This is a red flag with a white stripe angled from the upper left corner to the lower right corner, as seen below.
The red and white scuba flag was invented by Navy veteran Denzel James Dockery and then later made popular by Ted Nixon of US Divers. Regulation requires the flag to be displayed while diving and the diver is required to stay a specified distance from the location of the flag, which should be mounted on the boat or buoy.