Keeping the paper towel wet

[alymcf]

Hi I'm new to snails and I know they need a bit of water, so I'm doing like my neighbor does and moisten a paper towel and put it inside the terrarium. I know the snail spends time on the towel and maybe that's why it dries up so fast. I can't seem to keep it moist. Every 12 hours I'm spritzing it again with water. My neighbor doesn't have this problem but she's got a smaller, more enclosed terrarium. Mine is 5 gallon with a mesh top.

Any suggestion for getting the towel to stay wet for a longer time?