How do they get this footage?
 

I was watching this show about shark fishing at http://myoutdoortv.com/show/marksosin/index.html, and when he catches this shark he has footage of him hooking the shark underwater and then he has footage of it trying to get away. The shark swam some god awful distance but there was footage of him swimming the entire way I was wondering if this was staged or stock footage or what?