Propulsion question of a different sort. Swimming

I'm not sure if this should go here but I'll try. I am curious if anyone has tried or heard of someone who has tried to make their own "Endless Pool" swimming treadmill. I know I could buy one from Endless Pool but I can't afford it and what fun would that be if I could. I wonder how hard it could be to adapt the lower unit of an outboard with a big slow turning propellor. I know I would have to seriously isolate the electrical parts from any water. Endless pool uses hydraulics. They want about five grand for a drop in unit so doing something for less has a lot of wiggle room. If it were warmer out I would anchor my boat, strap a milk crate over the propellor and very carefully try swimming behind my outboard for some first hand research. Any thoughts- Todd

 

I would think a prop large enough to do that would cost more than five grand, why not search for industrial pumps and do the plumbing?