Mud

bedrock

Mud is a decorative block obtained by using a water bottle on a dirt block.

Breaking
Mud can be broken by hand, but using a shovel speeds up the process.

Obtaining
Mud generates in the mangrove swamp biome, and it can also be obtained by a water bottle on dirt, coarse dirt, and rooted dirt, transforming it into a mud block.

Usage
Entities standing on mud sink 2 pixels into it, similarly to soul sand. Unlike soul sand, however, mud does not slow the movement speed of mobs or players that walk on it.

Mud, not being a full block, has some unique properties; falling blocks such as sand drop as an item when landing on it, a hopper that is under a mud block can collect items dropped on it.

Most blocks that can be placed on full blocks can still be placed on mud.

Renewing clay
If mud is placed directly above a block that has a pointed dripstone underneath, it will eventually turn into clay.