More information, and a picture in the water...
The car is a 1960 ID 19, which was transformed by Kurt Fähnrich in 1968. The bottom and sides of the car were sealed. The back window and the trunk cover were of one piece and served as the car's only door. In the water, the car was powered by an outboard motor, on land it still used the original ID 19 mechanicals. In 1970 the car got a German TÜV, allowing it to be used on the road!
Later the car was updated to sail on open sea. As the outboard motor was not strong enough, Fähnrich used the ID 19 motor which was moved in place of the left front seat. With this vehicle he sailed around Helgoland (this is a little island near the German coast). In 1984 the car was given up and went to a junk yard. It was discovered there by a Citroen fan living in Hamburg. He bought the car and stored it. In 1993 it was offered for sale, but nobody was found with the time and money to restore it. The car was scrapped in about 1994.