It's actually a fake, when he kicks away the shark it swims off into the murky depths of the shore that he gets to very shortly after, for that to be real there would need to be a sheer drop right at the beach line and he and the shark would both have to have swam in the same direction, would you swim right after a big ass shark like that? And would a big ass shark like that swim head first into what is presumably a rock wall?
Also there's some noticeable effects stuff happening that is pointed out in the comments.