I first heard about the Wasp knife few months back from our fear mongering friends
in the British media. They seem to feel this will be a major problem in the streets of England soon. Since carrying a little pocketknife like the one I have with me every day is a social sin more serious than attempting to buy nuclear material in the United States, they get pretty upset about anything that might upset the Orwellian state they seem to love so much. This is the country that is attempting to force people to buy a $150 kitchen knife with no point, because, you know, if you had no pointy kitchen knives, no one would ever get hurt.
The Wasp knife is a personal defense knife for divers. The idea is that you would stab a shark with it and then inject a large volume of CO2 gas pressurized to 800 psi into the shark, presumably blowing it up or something. They state that it will cause the fish or whatever to rise to the surface before blood begins to leak out of the animal. I really wonder if the wasp knife's inventor has ever attempted to use this. Due to the restriction of a wet suit and the water, making a real stabbing motion is not easy and anything you need to defend yourself against underwater is a lot faster and meaner than you are. Being that they are more than $400 a piece, I am pretty sure you could get a more effective weapon for that price. Like a 12 gauge bangstick for example. At least that gives you a little distance from your attacker. I'm pretty sure this is just a gadget for people who wear $15,000 watches and like to pretend to be tough. Their website seems to think otherwise though and makes the case that most of the military need a $400 knife.
Frankly, this seems like a really stupid idea to me. It is worth mentioning that sharks very rarely attack people, and that the chances of using this on a shark that would attack you is vanishingly small. Most shark species want nothing to do with a person and the ones that do can pretty much tear a chunk out of you before you know what is happening. Sharks have not survived for 300 million years to be killed by a neoprene covered monkey with a knife full of cold air. And if the inventors of this little toy would like to prove me wrong, they can jump in the ocean and kill a Great White with it to show me how wrong I am. The guy who invented the modern bullet proof vest shot himself in the chest like 1000 times. Consider the gauntlet thrown.