Cut your sponges lengthwise into four equal pieces.
Arrange the sponges, so you have four on the bottom and another layer of four on the top.
Squeeze them together by the middle and wrap a rubber band around the middle tightly to prevent them from falling apart.
Gently pull and twist the ends of the sponge pieces to form a ball shape.
Place the water bombs into a large bucket of water and have fun tossing them at each other.