3. Fight Back
Once a shark takes hold, the only way you're getting out alive is to prove that it's not worth the effort to eat you - because you're going to cause it pain. Look for a weapon: You'll probably have to improvise. But any blunt object - a camera, nearby floating wood - will make you a more formidable opponent.
Often repeated advice has it that a good punch to a shark's snout will send it packing. In fact, the nose is just one of several weak points to aim for. A shark's head is mostly cartilage, so the gills and eyes are also vulnerable.
4. Fight Smart
Unless you're Rocky Balboa, you're not going to knock out a shark with a single punch. Not only will a huge swing slow down in the water due to drag, it's unlikely to hit a rapidly moving target. Stick with short, direct jabs, so you increase your chances of landing a few in quick succession.
5. Play Defense
Open water, where a shark can come at you from any angle, is the worst position place you can be. Get anything you can to back up against, ideally a reef or a jetty. If there are two of you, line up back to back, so you'll always have eyes on an approaching attack.