The first idea was using a fin at the back, additional coming out of the water independent of the snorkel. The advantage had been that the belt would run idepentend from the snorkel and didn't need to be adapted for different snorkel forms. Another idea was to keep the weight near the body. But there were disadvanteges : First a bigger system has to be designed to stabilize such a system on the back, resulting in more weight, worse aqua flow (especially when crossing waves) and an overall bigger belt. Furthermore for safety and better encapsualtion the system should be as small as possible and kept mostly above water, which works well with the snorkel extension. As an additional benefit, the battery is now in the missle inside and double encapsulated, as well as far away from the head for safety concerns. Therefore, the first and already milled system was not used and components further reduced (less vibration motors, no audio).