More news. I called a company that makes all kinds of foam products. They advised me that there are many companies that make closed cell rigid insulation boards. I asked her if she could get closed cell "marine" flotation foam and she said that she could but the Foamular stuff is the same. The only difference would be the density of foam and the color. The insulation companies color their foam for marketing purposes. Owens corning pink, dow corning blue ect. She also said the foamular should not absorb water and would be appropriate for my intended use.