Any time man ventures into the ocean he is in the shark's territory. Many sharks don't live in warm waters, but they do cruise through them to get to their current season's feeding grounds. Also, if they are hungry enough, they Do go into waters they normally wouldn't.
You never know when one of them is going to mistake you for a possible meal and take a bite. If you are willing to take the chance, it's your fault if anything happens. Not the shark's. Remember that. They are doing what they do naturally. You are an invader in their natural habitat.