I think the sharks are only biting us because surfers keep punching them. Every time some surfie dude has an encounter with a shark you hear that they punched it. Why? Most sharks would like to have a good fair fist fight but sadly god didn't kit them out with fists.
Of course, some would mount the argument that they don't go around biting sharks so sharks shouldn't bite them. But is this really the case? When you buy fish and chips you usually get a mysterious fish called flake. Flake is just a fancy made up word for shark. Over your life time you've probably bitten in to hundreds of sharks. I reckon if a shark wants to have a nibble on your leg you should just accept it.
You wouldn't challenge a cripple to a running race so why punch a shark?