https://www.gamespot.com/articles/minecrafts-first-aquatic-expansion-is-out-now-on-p/1100-6459079/

Dreaming of the deep blue sea? Quench all your marine needs with the first phase of Minecraft's latest Aquatic expansion, now available on Xbox One, PC, and more.

Now when you dive under the watery blocks of your Minecraft world, it won't just be a blue abyss with scattered temples here and there. Now you'll see dolphins, new types of fish, corals, kelp and sea grasses, buried treasure, and more. The seas even coordinate with the nine different biomes now too. For the full list of features in this first release, head on over to the announcement post.