I'd be interested in it if there was a playertype or some sort of Add-On that would allow me to not float in water, and have normal movement at the bottom (perhaps slightly slower movement, higher jumping?).
You could do an ocean build without that, since you'd build without water and then turn it on when finished, but I never really like building things just to look pretty. For me they have to be explorable, or role-playable or fightable in.
I always wanted to do underwater stuff when we had maps, and build underwater cities to play in, but just the fact that you're constantly crouched in order to even be under there was a nuisance.