The guy you are referring to regarding fending off the Great White attack on the scuba diver is Greame Duanne. That clip used to be posted on the web somewhere. And I will see if I can dig it out.
He is currently making another series of spearfishing videos ... so stay tuned. There used to be a short clip at his home page of handing off a Great White that raced up to his boat ...
http://www.digistream.co.za/stock.html