Sponges are the simplest form of multi-cellular animals, or animals that are made of more than one cell. Most sponges live in shallow water, but some live deep in the ocean. If a piece breaks off of a sponge it will grow into a new sponge. Sponges eat small pieces of food by pulling them through tiny holes in their bodies. The skeletons of some sponges can absorb water when they die. People sometime use these skeletons for bath sponges