Iowa Admin. Code r. 571-83.5
The "International Diver's Flag" (a red flag with a white diagonal stripe running from the upper left-hand corner to the lower right-hand corner, minimum size, 12" x 15", with a 3 " stripe), shall be displayed by each diver or group of divers on a buoy, float or boat during any diving or underwater spear fishing activity. This diving flag shall be displayed on the water only when underwater diving activity is in progress, the diver or group of divers must stay within a 100-foot circle of the flag. Recognition of this flag by law will not be construed as conferring any rights or privileges on its users nor be construed as restricting the use of the water so marked. Operators of boats shall exercise precaution commensurate with conditions indicated.
Iowa Admin. Code r. 571-83.5