The wife & I are looking at Hancock Fabrics. Upholstery fabric with a batten between the foam and outer material. Commadore was our final choice. I dont think salt or fresh
water makes an issue. Something like scottchguard? They were very helpfull and even
have classes on sewing. I've never sewn in a zipper. Good luck with your projects. If
I can figure out how to post pictures of our progress I will. jimbob