A sponge is full of holes but still holds water. A sponge is a type of porous material. The term porous means that there are tiny holes or pores in the material. When a sponge is placed in water, the water is drawn into the sponge through the pores. The water is then held within the sponge by the surface tension of the water. The surface tension of water is a property that allows water to stick to itself. This is why a sponge can hold water even though it is full of holes.