Salt water in the rocks, you don't have to worry about rattlers, coral snakes or copperheads. So that leaves moccasins. But do moccasins hang out around waves and saltwater like that? I don't think they do. It's entirely possible that the environment at that area doesn't harbor venomous snakes. Also, some people have learned to immediately ID a water snake from a moccasin at a glance. I myself need a few seconds to look. Maybe she doesn't.
Letting them bite her though, that could cause infection.
Did some checking and this was filmed on Lake Erie that is a freshwater lake. These snakes come out during breeding season that is why there are so many.