Fight Back: When a shark wants to eat you, you'll know in advance: It will hunch its back, lower its fins, and rush at you in a zigzag pattern. Thrust your spear gun, camera housing, dive knife, or anything else you're packing to discourage it. If you have a surfboard or body board, use it as a shield. If you are swimming and completely unarmed, punch the shark's supersensitive nose or stab at its eyes or gills. If the shark bites into you and begins to drag you underwater, don't play dead or give up. Get aggressive and do some damage to the shark. It might just let go.