In my experience with this game, the defining feature of the Ocean biome is the depth of the water. If the water is not deep enough to be an Ocean in any one spot, the biome is whatever the program assigned to the water-covered land at world generation.

Quite obviously, it cannot be a Mountain biome but it can be Meadows, Black Forest, Plains, or Swamp. I have sailed over each of these four biomes on water deep enough to float a raft, karve, or long ship.

There is a limit on the height one can raise or lower any single bit of land vis-a-vis its location at world creation. I suspect that the depth of water which is required for an Ocean biome exceeds this limit. Only a programmer familiar with the game's coding would know for sure.

As or those other biomes, one could conceivably raise Meadows, Black Forest, Swamp, or Plains high enough to be above sea level. One have to raise a sufficiently large tract to support spawning and then wall it off from the surrounding area to prevent migration by creatures spawned elsewhere. If one raised and walled off a sufficiently large tract of underwater Meadows and deer or boar appeared inside the walls, the answer would be Yes.

Again, I believe it would depend on what actually happens when a world is generated. Are spawn points established in submerged biomes for creatures of the land and air? If so, are the spawning points disabled because they are submerged?