Initially, I thought this was just another old car but then I read the history of it.
It is an Amphicar, built in Germany from 1961 to 1965. I had never heard of them. There were only 3,878 manufactured.

The story goes that President Johnson used to like to surprise his guests by driving them into a lake and then yelling "The brakes don't work! We're going down!" Then of course the car would start floating. He was quite the practical joker.

I looked these up online. They all look exactly like this one, just different colors.