Terry, I enlarged a shower on a Marine Trader 44, using exterior (textured) cement housing board in wide panels, attached with wall board adhesive. This material is totally impervious to moisture. Be forewarned that it eats up saw blades! Per Mark Ricter's advice, I finish coated it with glossy Sherwin Williams two part cement epoxy. The shower always looked new, shiny, and was easy to keep clean. Some of the recommendations mentioned here take so much work, you might be better off with lining the enclosure with green board, putting on a coat of epoxy, and then using small tile to finish off the project with a professional look of a residential bathroom. Only problem I could see is that you would have to constantly fight mildew. The cement board solution was the best one for dealing with mildew, which every shower has with Florida's heat and humidity. Martin Veiner ____________________________________________________________ Digital Photography - Click Now. http://thirdpartyoffers.juno.com/TGL2131/fc/BLSrjnsCN43cqRBq7KHlLrQJXgHuzgrLO rg8ovARn1GXMNNrdYjA7G7sB4c/