Sponge

Sponge is a block which currently has no uses other than decoration. As of the update, sponges have a new behavior and a variant, wet sponge.

Obtaining
A sponge can be obtained by drying a wet sponge in a furnace, which is obtained by defeating Elder Guardians, as they always drop one unit of this item upon defeat.

Drying
A wet sponge can be dried in a furnace making the sponge reusable. If a bucket is placed in the fuel slot after the fuel is used up, including if the fuel was lava in a bucket, the water will drain into the bucket. This is currently the only way to get the water back.

Usage
Prior to 1.8, Sponges had no use but decoration. As of the new update, sponges will absorb a 5×5×5 area of water around themselves in a "sphere". The sponge must be directly touching a water source to absorb water, and will only absorb water connected to an adjacent water block touching the sponge.

When a sponge absorbs water, it will convert to a wet sponge, which is darker, drips water, and is unable to soak up any more water.