When I was about 8-9, they had cartoons on TV called 'Supercar'. It was a flying car that could go underwater. I was impressed so much that I tried to build my own Supercar outta junk pieces laying around the farm. I failed. You can still see 'Supercar' if you google it.
I have a car that will go underwater down the local boatramp it lasted for 20 seconds so I think it qualifies, the recovery was expensive and there were jellyfish in the glove box