Please excuse the pictures, my good tablet bit the dust recently and my current ones camera is only 2mp.

Going with foam board with fiberglass covering, will be my first attempt at "glassing".
Center mount gearbox with a steerable out drive, and a stock prop off a Traxxas Villian.
Powered by a axial 27t motor.
Its getting a A frame winch on the back deck and forward superstructure.
Overall dimensions are 30"x12" rear deck will be 12"x12"
Batteries will be mounted in the superstructure with the ESC and receiver up top in their own waterproof box.

Inspiration..

The design will be modified a little.

The pontoons and deck are roughed in...