Your enemy will not be getting the cardboard wet (easy to avoid by thorough, systematic covering w/duct tape) but in building a strong enough wall to withstand the force of the water.
Can you use cardboard tubes? This would by far be the strongest thing out there. In fact, a boat MADE of heavy wrapping paper tubes would probably be pretty damn solid. But that might be bordering on cheating, because some of the "Cardboard tubes" out there are really pretty serious pressed-paper products.
Otherwise, I'd suggest looking into making some I-beam type structures to ensure rigidity on the long walls.
If anything goes, you should go to home depot and look into "sonotube" - the cardboard tubes they use to pour cement columns in parking decks etc. You could EASILY build a pontoon boat with those!
Or, you could always ask google, which immediately sent me here: http://www.gcbr.com/port.html
Can you use cardboard tubes? This would by far be the strongest thing out there. In fact, a boat MADE of heavy wrapping paper tubes would probably be pretty damn solid. But that might be bordering on cheating, because some of the "Cardboard tubes" out there are really pretty serious pressed-paper products.
Otherwise, I'd suggest looking into making some I-beam type structures to ensure rigidity on the long walls.
If anything goes, you should go to home depot and look into "sonotube" - the cardboard tubes they use to pour cement columns in parking decks etc. You could EASILY build a pontoon boat with those!
Or, you could always ask google, which immediately sent me here: http://www.gcbr.com/port.html
