Looking at the pictures on the website, and watching it in operation, my guess is that the pedals drive a generator and that in turn feeds an electric motor in the rear hub, with a chain drive from the rear wheel to the prop. The front wheels steer when out of the water, and have disc brakes. The prop is turned to provide steering in the water.
The efficiency of converting power via electricity from motion, back into motion is going to be pretty poor even just to move it, and is probably incredibly dire when moving it when in the water. It looks like it'll move it on the flat, and can probably get some speed up with enough time to build some momentum up, but doesn't have enough omph to even get up the slight incline when it needs to leave the water.
Essentially it's a dancing bear.
