The oddest and most unconventional contender – probably for any aerial competition – was the Piaggio-Pegna PC.7. Instead of floats, Piaggio went with hydrofoils – hoping this would reduce drag and weight.
The aircraft was intended to float deep in the water, with the wings resting on the surface (whether the photo above shows the prototype resting ‘naturally’ is unclear). The engine had an extra shaft and clutch controlling a water-screw at the back. The plan was for the aircraft to first operate using the water-screw and a lower rudder – like a boat. As it gained speed, the hydrofoils would generate lift and raise the aircraft, clearing the main engine/propeller above the water. The pilot would then switch to conventional controls, and the main engine clutch would be engaged…
The PC.7 never flew. Although theoretically possible, the control/clutch configuration would have required a pilot with more than two arms..
Hydrofoil: comment ça marche ? https://en.wikipedia.org/wiki/Hydrofoil