If you check out the behaviour of the tiger shark in the vid at
http://video.google.com/videoplay?docid=4021480117524944318&q=eric+cheng&hl=en you'll note it swims past a group of divers and then gets real up close to a lone diver in the background. That shark is actually checking the diver out and thinking "can i eat him ?"
Taken from Wikipedia:
The tiger shark is second only to the great white in number of recorded human fatalities [2] and is considered, along with the great white, bull shark and the oceanic whitetip shark to be one of the most dangerous to humans. [3]