If given some option of 'Other', I would say "water absorption", whatever the technical term is called.
Basically, like the biological version of Atlantion, the hydroelectric-powered land I created, that's based underwater.
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)