An item referred to the German magazine Marine Rundschau dated December 1922 in which a former commanding officer of a cruiser submarine described the possibilities of building a battleship submarine. Main issue were the problems dealing with diving and while submerged sailing. Due to their size was the overview on board not clear demanding extreme high performances of the personnel. Preparing for diving and checking all closures according to the German regulations would take 90 minutes. The author concluded that although it was technically possible to built a battleship submarine but this type was useless as warship.
