Dreaming of sharks can have a variety of meanings. It could represent a predator that's taking a toll on your life. It could be in the form of a relationship, a friend or your job. You could be involved in something where you're in over your head. It can can also mean that you have some uncontrollable or irrational fears.
Well, it could mean that someone is trying to control you or destroy you. Or you could be running from fears and they are just coming out in your dream. I would consider figuring out your fears and dealing with them.