Well done - these guys did a nice bit of editing, I'll give 'em that much, enough that I am not 100% it's fake, but here's the evidence I think it is.  I used to work for a tourist company filming at the Farallon Islands and I quickly had to learn how to blend in my footage from South Africa to match with the murky waters of the Farallones so it appeared as though these tourists enjoyed spotting great white sharks from their view in the cage (all for their souvenir DVDs) Yes, I'm saying I have faked footage and yes I'm saying that 95% of the time you DO NOT see white sharks on cage-diving trips to the Farallones so consider yourselves warned before you shell out the $900.
Anyway, heres' why I think this video is fake.

• Visibility: How deep is this harbor?  I can't see the bottom in any shot, nor can I see the rocks of the cliffs even when he's getting out.  I know it's a steep ledge so I can buy that it gets deep quickly, but if the water is clear enough to see the shark at a distance and even beyond the shark, why can't I see even a hint of a rock or ledge anywhere underwater, even when he's getting out? Maybe because the footage is from a cage-diving trip out in the open ocean...
• Scripting error:  Why is be being high-fived and called a hero before he even gets in, then later a guy shouts "Shark!" as though it is an unexpected encounter?  Is all the hype just about the medium high jump?
• Timing: Immediately after the jumper surfaces his buddy has spotted the shark and the videographer just manages to get a clear shot of his buddy pointing.  A little convenient.  The shark comes into frame right after as well. Convenient again. He swims for a bit, then turns around and the shark comes into frame again right on queue. Again, too convenient. 
• Swimming: Why isn't he making any progress toward the rock as his arms are shown to be swimming (the first round of swimming?) Maybe so he can turn around for one more good shot, at which time the shark kindly shows up on queue as stated above?
• Oh, and I guess the fact that two different sharks were used in the spliced footage is pretty good proof.  Check out the video above.