The official site says:
As divers, we all know what the effects of compressed gas are underwater. Our training teaches us that our lungs would burst from over-inflation if we held our breath and rose to the surface. This principle is key to the effectiveness of the WASP Injection System.
This weapon injects a freezing cold ball of compressed gas, approximately the size of a basketball, at 800psi nearly instantly. The effects of this injection will drop many of the world's largest land predators. The effects of the compressed gas not only cause over-inflation during ascent when used underwater, but also freezes all tissues and organs surrounding the point of injection on land or at sea. When used underwater, the injected gas carries the predator to the surface BEFORE blood is released into the water. Thus giving the diver added protection by diverting other potential predators to the surface.
Here's video of one taking down a watermelon. Permanently.
You can buy one here. They ain't cheap. Via Bruce Schneier.
*Previously: Urban Security Suit by Tim Smit.