Treated marine grade plywood should do the trick, Rhino on top would probably be ok, or after it dries good something like thompsons water seal, but a word of caution, if you totally seal the wood then if any water ever does get in (and it will), it doesn't have a way out, so it'll rot the wood faster. Thats why you don't seal the bottom of a deck. My friend ("E", on the SC board) just redid the deck of his pontoon with recycled stadium seating (aluminum). Way lighter and stronger than wood.. Hope some of this helps. Scott (BAMBAM, SC board).Originally Posted by MAINEIAC