Having considered the design implication, It became clear that by taking a number of inventive steps from this basic concept, an inexpensive shallow dive mini sub could be easily manufactured using our existing production tooling.
Abstract
Based on marginally positive buoyancy, such a craft could be driven into the water and remain topside until the throttles are opened and three axis Joy Stick pushed forward operating down planes and pulling back on the stick to return to surface, with turn and spin controlled by the main Thrusters.
Due to the positive buoyancy bias, the craft would automatiy return to the surface in the event that the motors were switched off or failed.
To add a high degree of safety both motors would automatiy switch off if the pilot attempted to descend beyond maximum DNE.