Wikipedia
Xploderz
Xploderz is a line of toy weapons made by The Maya Group to compete with Hasbro's Nerf Super Soaker line and marketed as a safer alternative to paintball. The ammunition uses what The Maya Group calls "H2Grow Technology", wherein the polymer pellets (containing acrylic acid, sodium hydroxide and coloring) grow into water pellets after being immersed in water for three hours. Unlike paintball pellets, the water pellets are biodegradable, easy to clean off clothing and will not cause any bodily injury.
The Xploderz concept is based on Orbeez, a girls' toy line also by The Maya Group that uses water-absorbent pellets.