Like hippo going to the toilet.

Finally, a garden tilling service that doesn't need a truck to haul around it's equipment.

how.. how does it do that without totaly wrecking the blade and the gearbox?

They don't call it a mud motor for nothing. This is sort of like this:

http://youtu.be/bKKzvtvzekY

Maybe it DOES eventually wreck the blade and gearbox...

The prop, yes.
The gearbox....there ISN"T ONE!!! These motors are usually direct drive to the flywheel, no gearbox at all. It's a motor with a shaft welded/bolted directly to the flywheel and a prop on the end of the shaft. You take it out of 'gear' by lifting the prop out of the water. (no reverse)

Go-Devil, mud motor, etc. Not that you are supposed to actually use them like in the video...

But as noted above, direct drive. Output shaft connected directly to the engine. Used a lot in the south for navigating very shallow water.