In theory Styrofoam is a closed cell product meaning that is water proof. In practice it tends to absorb and hold water It can take months to dry out very saturated Styrofoam.
As a rule Styrofoam goes in boats to provide flotation. In many applications the Styrofoam is in locations where water tends to pool and is difficult to completely remove.
I found several forum posts about ways to waterproof Styrofoam. Essentially use a paint that will not melt it, to seal the Styrofoam.
My question is will attempting to seal the Styrofoam, prevent water absorption or will it still allow some absorption and make drying it out even more difficult?