Alpha Flag and Diver Down Flags
Divers have adopted a red flag with a white diagonal stripe which is legal in some states on sole state waters. In most states, including Wisconsin, the red flag does not have any legal status identifying the boat. Wisconsin law requires the use of the red flag with the diagonal stripe to identify the diver in the water more than 150 feet from shore. This is to mark the diver's location not the dive boat per se.
The "diver down" flag must be red, 12 inches high and 15 inches long with a diagonal 3 inch wide white stripe. It must be high enough above the water to be clearly apparent at a distance of 100 yards. Wisconsin, unlike federal rules, does not require that the dive boat be marked. It only requires that the dive location be identified. At night on sole state waters, the boat's white anchor light would be used.
Except in the case of an emergency, a Wisconsin diver may not surface outside a 50 foot radius from the diver down flag. A motor boat is prohibited on Wisconsin waters from operating within 100 feet of a diver down flag or a swimmer unless the boat is part of the diving operation.
Consequently, the prudent diver when operating more than 50 feet from the dive boat should tow a diver down flag and surface within 50 feet of the flag.