So I was testing out Serpent in a 2.1 pre-release to see what happened, and discovered that solid 3D floors underwater don't display the liquid above anymore (see screenie). For moving 3D floors this will only happen when it's completely submerged. (in all cases it still works fine when you're underwater and looking up at it)
I dimly recall some kind of limitation with this a long time ago, but it never affected these maps until now. And in any case, 3D floors rising/lowering in and out of water is a perfectly rational thing to do in any GZDoom map
