This is just a what-if scenario. My diving is not dominated or overshadowed by fear and thoughts concerning shark attacks. I do recognize the low probability concerning such an event. This is just one of those things that I wonder about sometimes, and I would suspect that many other divers do also, on occasion.
Ben
Believe me I've thought this over in my head, even before I even thought of getting certified.
IMO I think the best bet would be to go for the eyes, nostrils or gills.
Sharks do have protective covers for their eye so I think targeting the eyes wouldn't be as effective as other areas. I do know that fish gills are just composed of thin cells to allow oxygen in the water to diffuse through. I'm pretty sure roughing this would be extremely uncomfortable for a shark.
And of course no person or animal likes fingers crammed up their nostrils.
Trying to punch or knife a shark underwater just seems to complicated. I don't think I could deploy my knife in that situation.
Just remember that all shark's prey can't really fight back. You don't have fish w/ 3 inch horns just roaming the sea. So any bodily intrusive attack would be a surprise for them.
Just my two cents