This toy operates on the principle of buoyancy. By varying the amount of water in the ballast tanks, a child can operate the submarine at any depth. The use of a hand-operated air pump and the twin-motor drive system minimize complexity and cost, by offering a wide range of maneuverability with few moving parts. I designed this hoping that children could run this in a pool or bathtub. Running at low voltage and current, the motors should be fairly safe. The propellers are shrouded, so there is little danger of injury from them. I would hope that this toy be made from a decent plastic so that it would last for a while. With a large enough scale of production, it may be possible to sell this toy for as little as $10-15.
Vicente Malave