This contraption started life as a 1957 BMW Isetta microcar. It is now powered by a WW2 era Lyoming aircraft engine, in a rig inspired by the airboats that ply the Everglades.  As I was setting up to take the photo, the owner yelled "Clear prop!", fired up the motor, and nearly blew me over.  Note the windsock and the red warning light on the prop cage.