Check out how these Aussies keep their composure as a great white shark circles them several times during their spearfishing outing. One of the guys had a head cam on and filmed the whole encounter. The interesting thing about this video is that the guys were snorkeling, not scuba diving. This changes things immensely in favor of the shark (as if it really needs any more home field advantage) because the guys are essentially tethered to the surface for anything other than a short period of time.
I grew up spearfishing in the Bahamas where you are not allowed to use Scuba tanks or spear guns. You are only allowed to snorkel and use a Hawaiian sling when spearfishing. This is for conservation purposes as it gives the fish you are hunting much better odds than if you had tanks and a compressed air or band spear gun. It's a good rule, but it can lead to situations such as these. More than a few times, my buddies and me bunched up in a ball, dangling from the surface like a piece of bait, with our spears pointing outward and fended off the advances of a nosy shark. I don't blame the shark at all. We were after all practicing our sport/hobby in their home and it was only doing what it should, scoping out the intruders in its midst. We NEVER faced off with a great white though and I don't know how I would have reacted.
I really have to admire the composure of these two guys in the video. Their relief is obvious when they finally get into their boat. I can relate to the feeling as it is one I have had even though facing off with smaller predators, who nevertheless could easily make a meal out of one had they so desired.