I was told that the original race cars leaked so bad they drilled holes behind the seat so under acceleration the water would drain out.
The floor plate has corrugations about 3/4" tall and that would be a helluva lot of water to carry around.
Ryan,
The MkI & Mk III road car chassis' holes were plated over and also had cowls covering the steering rack exits. There was also a large plenum on the top scuttle.