In the words of Crocodile Dundee, “That’s not a knife, THIS is a knife!” C02 delivery system in a knife. Only problem with sharks is if they attack, you generally don’t know it until after a bite has been taken out
I've heard about the WASP knife before. I believe it was intended as an anti-shark divers knife. The idea was that once you stabbed the shark, by pressing a button on the handle you release a CO2 charge that injects through the blade, causing severe damage to the animal. You'd need a pretty clean stab, and that shark would have to stay awfully still while you press the button... There's some videos floating around in YouTube, I guess I wouldn't want to be stabbed with that thing and injected with CO2, but then again getting stabbed with anything is a bad idea in general.
The WASP costs 500 USd, and other than injecting CO2 its not a particularly good blade from an utility perspective nor is it that good a defensive blade either (other than the shark killing injection concept).
Let me know what you guys think in the comments below, but I think there's lots of better things in which you can spend that kind of money (unless you need to blow up sharks, of course)