The problem is if you get bit by a little fish that makes you bleed and that provokes a bigger one that can do serious damage. I've seen sharks and cudas aplenty and they've always ignored me...but I've never been bleeding around them or around a feeding zone.
However, an absence of proof is not proof of absence, you can't prove a negative. So whilst no one I know has ever been attacked by one, I know that they do attack people. The question of frequencies is hard to figure out since it's so dependent on multiple factors such as season, density of people/fish, individual circumstances, and so on.
Are people attacked by sharks just because there are more of them where the people are, or because they're more aggressive? If every one of them was replaced by a barracuda in the same situations, would the bite frequency increase or decrease? I honestly don't know.