floating car

What would it really take to make a car that wont sink? I think a little innovative engineering could make this reality in every Ford vehicle. Foam is being used more frequently as sound deadening, and it also has a floating effect. Cars are being designed so that they are more and more tight so that they are quiet and comfortable inside the cabin. With these two features already in place, there should be some way of making a normal car float, to the extent that the passengers wouldn't die in the case of flood, tsunami, or driving into a lake or river. It would make for a better cabin at the same time.