MC, I haven't a clue..........! As I said, my aim is to keep the water on the outside. I am not the least bit interested in having the interior filled with water and then depend on my Styrofoam logs to stay afloat. Keep the cork in the bottle: and the water on the outside of the bottle, and the bottle will keep floating! Yes, the Styrofoam will do a bit of crumbling, so if you want a clean boat, get rid of the Styrofoam! Connie