@sun If a shark is actually attacking you, you don't have much chance - the end result is almost like to be what happens when a shark attacks a seal successfully.

Many cases of shark "attacks" seems to be sharks wondering what's in the water and as that is really their only means available, to test that out, sharks give things a bite - usually the shark determines that the thing is the water is too bony to be worth eating and so swims off, but the frail human body doesn't resist getting bitten very well and thus usually proceeds to bleed out.