A diver down flag, or scuba flag, is a flag used on the water to indicate that there is a diver below. It is red with a white stripe from the upper left corner to the lower right corner, and was designed and introduced in 1956 by Navy veteran Denzel James Dockery. It can be placed on a boat or on a surface marker buoy. Practice about this choice of flag is not uniform worldwide. In some countries, the practice is to use the Signal flag ALFA/ALPHA instead.