When the sponge 'soaks up' water, it makes a sound similar to breaking stone, and gives off water particles. Which doesn't seem right.
Linked issues
duplicates 1
Comments 12
Confirmed in 1.8-pre2. If you hack in a water/lava source block and place it (or have a wither break water/lava), you will also hear the stone sound.
merged with MC-91091
the particles are intended as the sponge became wet