The initial prototypes and development were made just down the road from my work.
We made quite a few parts for them , the production versions look somewhat different to the units I saw and supplied parts for.
The guys were always flying off to the states to get the thing into production.
Car and Driver, upon testing the Amphicar, a West German answer to a question few have dared-ask, said it "handled like a boat on the road, and a car in the water." An apt description. The last shot is surely a rare event these days, two Amphicars passing on the water. But I guess in Homer Simpson's city, it's a common occurrence.