I have no doubt that parts of the video are, indeed, real.
I also have no doubt that parts of it are really unwise.
Of course, knowledge is very powerful, and the more one knows about the wildlife with which they interact, the less likely thay are to be injured. After all, Steve Irwin spent his whole life playing tag with alligators. There is a difference, though. Steve usually didn't quite meet the gators on their own turf (the water), but chose to stay on land most of the time and "wrestle" them there. That gave him a slight (many times, VERY slight) advantage. These divers are on the shark's home ground, and I firmly believe that if that big boy decided he really wanted to sample an arm or leg, the swimmer would be lunch.
More adrenaline than this ol' boy needs.