Well, you can if you start a new world make a super flat world and then click "customize super flat world' Then go and click on "water world" of your the list of other types of worlds. I hope this Helped
Oh, and I was wondering if your good at building or using command blocks because if you are a master builder or extremely good at command blocks I could really love to use your help for us together to make a Marvel Cinematic Universe Map. Credit will be granted
