This is actually pretty common now (maybe still stupid, but its done). Alot of the whites in S. Africa are pretty tame do to all the feeding while researching, and are just looking for an easy free meal. Theyve also discovered (who was the first to try, I dont know - but they sure were lucky/stupid) that a great white can basically be paralyzed by grabbing its snout. I saw it on shark week - their mouth flies open, membranes drop over the eyes, and they just freeze. That looks like what this guy is doing.
Still, Ill never do it.
Brian