Me lord of the high seas! Foam technically? I am to assume ney not so! so rather than gets us all into the kinds types and density levels offering none other than the best cushioning even tested 'pon curve. (Either, Ester, Urethane, Styrene, Ethylene and set up foam in place) HOWEVER
I'm thinking of the foam that lingers 'pon seas surface following a waves breaking and a hulls parting.