A production car/boat hybrid was made in the early 60's. I forget the name. It was a boxy little convertable with a high wheel base that allowed for two propellers and (I guess) a rudder. You could drive it into the water, switch the power over to the props, and off you went at a couple of miles and hour. It had a convertional gas engine with a watertight engine compartment, cab, and whatever. The first time I saw one of these on the water I completely flipped!

I think the problem was that it was neither a very good car or a practical boat. It was very cool, though.