Once while camping at Jenny Springs in Florida, I looked out in the
river to see a guy going up river using a DeWalt cordless drill in
which he had chucked a prop for an electric trolling motor on a long
shaft.

wrote:
Once while camping at Jenny Springs in Florida, I looked out in the
river to see a guy going up river using a DeWalt cordless drill in
which he had chucked a prop for an electric trolling motor on a long
shaft.

That's an idea. One of those large drywall compound mixers might stand
in as a propeller.