This data pack removes all land above sea level leaving only water and ocean biomes.

It achieves this by setting the continentalness to -0.5.
This is the only data pack/mod i've seen that turns the world into an ocean for all versions from 1.18.2 to 26.1.2
Originally from The Water World modpack!
Quick facts
- Edition: Minecraft Java
- File type: .jar
- Minecraft versions listed: 1.21, 1.19.3, 1.20.2
- How to install: Install the matching mod loader (Forge, Fabric or NeoForge) for your Minecraft version. → Download the .jar. → Put it in the .minecraft/mods folder and launch that loader profile.
- Where to get it: Opens on CurseForge — not every file is mirrored on our own servers.
Install steps are the general flow for this file type — see the MC Java Mods guides for the full walkthrough.
Water World (Only Ocean) is a free Minecraft Java datapack. Compatible with Minecraft 1.21, 1.19.3, 1.20.2, 1.19.4 and newer. Downloaded 5,036 times (via CurseForge). Download it and open it directly in the game.