MuddyWaters

Dirt blocks that sit under water gradually turn into mud, and the shoreline grass around a biome is converted into the biome's mapped shoreline blocks such as coarse dirt, cobblestone or podzol. Source water converts the dirt beneath it after a delay of about 5 minutes (6000 ticks), while flowing water takes longer. Dirt next to mud converts a little faster, so the change spreads in patches instead of all at once, and the result looks more organic across a whole waterlogged area.

The mod is meant for worlds where mud looked strange as the blocks beneath water, and it converts only generated and loaded chunks without touching world generation. It requires Cloth Config API, Fabric API and Mod Menu, all three of which must be installed. The environment is server-side only, so the conversion happens regardless of what clients run, and the license is the MIT License, though the mod is not open source. Files are published for Fabric only, for game versions 26.2 and 26.3, with 1.3.0 for 26.3 as the latest file, and an issue tracker is linked.