The Reid Flying Submarine

More pix and article here.

It wasn't a high-tech machine, despite its abilities. In the air it was powered by a 65 horsepower four-cylinder Lycoming engine. While underwater a 1-horsepower electric motor provided propulsion. Conversion from aircraft to submarine was a clumsy affair. The pilot first had to remove the propeller, and then cover the engine pylon with a rubber diving bell to keep the engine dry. The pilot used an aqualung to breathe. Maximum depth was roughly 10 to 12 ft (3.5 metres).

From THE SATURDAY EVENING POST for January 1, 1966.