Since batteries are so heavy a ski boat will have to be designed where they are removable. The weight is okay for a surf and wakeboard boat, but not for a ski boat. The batteries would have to be designed to be a bunch of small removable modules. You could buy enough of them where you could use the boat while some of them are charging and just keep swapping them out. The electric Ski Nautique prototype is a good start, but the entire interior is taken up by the battery. You would only need the electric motor, cooling system, cruise control, and going from forward neutral in and reverse would just be tripping a switch. The rest of the spaces that would be taken up by the engine and fuel tank could be used for batteries.