Not at all. Sharks are not anything like they are portrayed on tv and in movies. It is a treat to see them underwater. They are not aggressive and are actually more afraid of you. If you move too fast they get spooked and swim away and you will not see them again.
Just remember the next time you get food out of a vending machine you are at a higher risk of death than dying from a shark attack. True fact:
http://www.buzzfeed.com/awesomer/20-things-that-kill-more-people-than-sharks-every#1yds2hm