Nope, not gonna talk about bat viruses, just an amazing knife I stumbleupon while browsing.
It has a CO2 cylinder which shoots a ball of gas into the shark or bear that is attacking you, rendering it well and truly ferked, and if diving, it has the bonus of floating the carcass to the top for other biteys to attack it while you discretely swim away.

If i still dived I would definitely love to have one of these puppies on my calf.
http://www.darkgovernment.com/news/knife-can-freeze-organs/

lol, I know what you mean Ammad.
I can imagine some spy/slash and bash film have some bad guy's guts explode all alien like after getting a prod from one of those things.

I liked the replies in the original post, where someone suggested they would like to make one, lol, like yeah, good luck with that happening.

Great idea for pilots, given the difficulties with guns on planes. Not sure about divers though. You need a bit of warning to use that thing, and you don't normally get that with shark attacks.

Actually, I have heard a few accounts like that too. However, in that situation, would you be getting out of the water, or getting out your knife? Remember that a knife can look a lot like a struggling fish.

They don't actually do circles, but they do pretty much the same thing. Of course, this depends on the situation. Great whites taking seals will come out of nowhere without warning. Bullsharks in dirty water will taste/look with their mouth. I think it is in situations where the sharks think the prey is not going anywhere fast and/or they are not confident enough to be the first to take a bite, which can be a risky strategy - getting bitten or knocked unconscious for a few seconds can mean death if there are predators around. In most situations, if you can see what is going on, the sharks will give you plenty of warning before biting. They start to move more erratically. I think they put their pec fins down too. I tend to leave when the sharks start hanging around, so I haven't done a lot of observing.