Yes they can swim just fine, just be warned that once they relax they like to "go" in the water... If you find PAM too expensive, go to a WalMart, Walgreen's, CVS, etc and pick up the NIX lice remover - there's a package that contains two 2-oz bottles. Mix one of the bottles with a gallon of water to make a 0.5% permethrin solution. Spray the snake's enclosure, substrate (whether paper towels or newspaper), and hides with that instead of PAM, allow everything to dry, and put the snake back. Do not spray the snake or the water bowl. As long as you keep the bottle of solution out of direct light it will remain effective for quite a while. Personally I would completely clean the snake's cage every time it makes a mess, and then re-treat the enclosure, hides, and new substrate.