I had a couple of liquid spills in the cabin and decided to keep such events from entering into the bilge. So I sealed the rear of the floor up to the quarterbirths. This would not, of course protect from a major event... but anything up to a couple inches of rain, or splash, or minor boarding wave would at least be kept in the cabin.
The rubber works great as a non skid step and doesn't smell like the carpet did. The paper roll holder is simple to do and a really convenient placement.
as always... here is an illustration
http://www.com-pacowners.com/4images/details.php?image_id=598
Dale