If navigating shallow waters is part of the boat's SOR's I come back to the paddlewheel idea. Using two rather standard bicycle wheels with hub drives rated at 1 kW each, one could have a pretty powerful paddlewheel "just" connecting the wheels with the right sized paddles on the outside rims. Such a paddlewheel could drive each of two Denney pivoting tender/sleds to turn the vis on a dime. There are already motorcycle wheel hub drives rated at a continuous 10 kW. There must be a good reason why I could not find not even a goofy example of such a construction yet on internet.

Luc