An particularly peculiar 'stillborn' from the archives, presenting the Herzog Conte Schwimmwagen....
Conte by Hugo90, on Flickr
For the Conte amphibious car, there are no borders at rivers, seas or coasts.
Even at low depth of water, the car swims and the drive goes on. The hydraulic twinscrew system with power steering gives sufficient speed to the car also in string flow in rivers.
The steering in the water is operated by the front wheels now freely standing and the twinscrews.
The landing and continuous driving is easy with the differential pawl built into every car - a short braking to dry the disk and drum brakes - and the drive goes on over land as in a normal vehicle.
Conte by Hugo90, on Flickr
Based on well-proven Ford mechanicals, this neither-fish-nor-fowl creation was to be available with the choice of the 110bhp 2.3 or 140bhp 2.8 litre 'Cologne' V6 engines. At this point I could make a very obvious BOAT-ANCHOR joke, but I will wager that you're well ahead of me on that one already. This powerplant would have given the vehicle a theoretical top-speed of approx 80mph on land, though that would probably demand quite a run-up and a certain bravery on behalf of the driver captain, given that it weighed 2.3 tonnes and, well, it looks like an ill-proportioned lego-car so you can probably figure out what the handling etc would be like...
In addition the thing came with independent suspension, locking rear diff and hi/lo ratio gearbox. I would imagine that this would be useful for hauling itself up slimy slipways out of the wet stuff rather than any pretension to 'off road' in the checker-plate-and-anourak sense.
It would appear that it never got past the prototypes as seen here in these brochure shots (it was also exhibited at Frankfurt in '79), which is hardly surprising given the historical success [or lack of] for car-boat combos which manage to be too expensive, and unappealing to both car types and boaties alike.
See also: Dutton Amphijeep, etc