VW Beetle creator Ferdinand Porsche produced the four-wheel-drive Kübelwagen
for the German Army in WWII. He then made an amphibious version of it in 1941, followed by a smaller version of the first amphibious car called the Schwimmwagen. It was powered by a 1.2-liter air-cooled flat four, which also drove a single propeller. The amphibious car used the front wheels as rudders when in the water. On land, the propeller would swing up, disengaging it from the engine. The Schwimmwagen was heavy and slow but had good traction off-road.
JasonVogel at en.wikipedia