I like the Minecraft oceans, I build underwater houses, explore caves, gather resources, etc. Sometimes, it's hard to do because I have to go up to the surface for air. I think in Minecraft, you should be able to make scuba gear so you can stay underwater for longer without having to go up for air after a few seconds. That way, utilizing Minecraft's waters will be much easier.
We're all living in a Yellow Submarine, Yellow Submarine, Yellow Submarine...