I feel guilty now, because I have bragged about that trike several times over the years. The wheels were full of plastic foam, which made it float. And the paddles were bolted to the inboard side of the rear wheels. It was actually a better boat than land-vehicle. It was built for Kinetic Sculpture Racing. One of these days I hope to find time to rebuild it.
Here is a smaller trike I built more recently. This one has been to Burning Man several times.
I try to give moral support to other trike builders!