I wanted to try this too, so I started a build.
Drivetrain is a sss56114 480kv with a 1:5 planetary gearbox.
Heere are some pictures
I wanted active steering so I added a rudder. The throttle and the steering will be controlled from the handle.
First run in the water was promising but torque is difficult. Maybe I will try to move the rudder more to the side.