Diver-down flags are used by scuba divers to signal other nearby sea vessels that there is a diver deep down. This is intended for safety purposes. If other sea farers see this, they should steer clear away from the flag at least 25 yards, maintaining a slow even speed. This is to avoid any collision with the diving boat, or accidents like being run through by big ships.
There are two types of diver-down flags as shown in the picture. The international flag is called the alpha flag which is characterized by white and blue colors. The red with white stripes flag on the right is used in North America.
