Personally I think it was a fantastic idea. It a different dynamic on movement having to consider what could be above, below, in front, behind, to the left or the right adds more depth to situational awareness.
Also the scenery was awesome. Much better than the same ol' trees and grass. All the underwater caves, and monsters which had never before been seen by the land dwellers.
Even the music was great.
Of coarse this is my opinion of it. I regularly see the opposite opinion on these forums though.
Tell me why you do or do not like underwater battles.
Simply saying, "because they are dumb" is not constructive. Give actual reasons please.