I would suggest you arm yourself with a good education about sharks. Sharks are not thoughtless killing machines like the dumbasses at the discovery channel like to portray.
I'd suggest you find copies of the documentaries Sharkwater by Rob Stewart and End of a Myth and Beyond Fear by Ralf Keifner in which he describes the body language of sharks. Then go find a no cage shark dive to go on.
Seeing that this is your first post, you have no logged dives and you are talking about swimming with sharks I'd suggest you educate yourself before you encounter a shark as the lesson the shark will teach you comes with a high price tag.
As I always say, Eventually everyone pays for their education, one way or another.
People have been attacked with "sharkshields" all they do is annoy the shark a bit, but if you are acting like food and smelling like food, they are going to take a taste unless you can communicate that you are not food.
If sharks are known in the area, after you spear a fish, put it in the boat, don't drag it about with you leaving a trail for a shark to follow to you. Leaving a trail for a shark is called natural selection and if you do that, I'm going to root for the shark to remove you from the gene pool. Sharks are endangered, humans are not.
Sorry if I sound like a jerk, but their is no reason to kill a shark. A little education and you'll see why. Now grouper, halibut and tuna, go wild, them's good eatin'