Sponge is a block notable in Classic and Indev for being able to erase water within a 5×5×5 area.
In Minecraft versions starting with Alpha it is a purely decorative block only attainable via Creative Mode or inventory editing.
History
Sponges are pointless unless you have dishsoap, which you can then use to shove down a villagers throat if they have a potty mouth.
Properties
Sponges do not need light to survive, and do not decay (sponges used to decay in the implementation of the 0.0.19a update, but this was changed within 50 minutes of the release). Sponges also use the same sounds as grass.
Uses (Classic and Indev)
As a building aid
A sponge can be placed around an area underground clearing the area of water. This can greatly help construction of underwater bases, homes, etc. After the player constructed the structure, the sponges can be easily removed.
As an anti-griefing measure
A sponge can be hidden in walls, floors, etc. as a defense against griefers. This can confuse and slow down griefers when attempting to flood an underground development, leaving more time for them to be caught and stopped.
In small rooms, this measure, when implemented in every corner of said space, can stop that room flooding altogether.
Uses (Infdev and later)
As a redstone tool
Note: This use has apparently been removed as of snapshot 12w07a, making Minecraft 1.1 the last official version with which this is usable.
A sponge can be used as a redstone object for updating blocks. If you place a sponge next to a block that needs to be updated, then remove the sponge, all blocks within a 5x5x5 range will be updated. This can be very useful for redstone builds using the BUD (Block Update Detector) switch, especially since it also updates areas whenever it is pushed by a piston.
Gallery
- Picture 2.png
An example of sponges keeping an area dry in Minecraft Classic.
Since the Adventure Update sponges are obtainable through creative mode.
References

