So went by my Lowes store to check these out. To me they are too soft. Really need something else that will hold its shape better. I feel they would not seal that good. There is a happy median between memory foam and close cell foam. Found a foam company that offers water resistant foam. Little harder than open cell, but enough give would form a good seal. Plus the added feature of water repellent.
https://www.foambymail.com/dryfast-foam.html