I've seen this guy on Shark Week. Pretty cool stuff.
But PLEASE understand he isn't just diving in with any shark. There is A LOT of prep work and "feeling out" with the fish before he gets in. Not to mention years of experience and research time with these animals.
Either way, this is a bit out of my league... Although, when you think about it, what's the difference between a 12' shark and a 12' dolphin? Both carnivores, both have teeth, and both out weight/power/maneuver you in the water.
But good find Juan!