I actually did a lot of reasearch on this ski concept, there is a company in Australia that will sell the designs for the engine but they will not produce them, engine weighs about 25 lbs starts rotation at 3 psi, a carbon fiber hull that would hold two carbon fiber air tanks inside. no fuel tank . no electronics, no exhaust, no cooling system , hull can be totally sealed so no need for a bilge system either. The air tanks are the flotation, they are full of air duh. I would make it so the air tanks are removable from the back so you could just swap them out, any dive shop would have the compressors necessary to refill the tanks or you could invest in a two stage compressor.