Nah, they're not. Reef sharks are fine. I've swum with plenty of them while diving on the Great Barrier Reef, and have seen a few Grey Nurse in Jervis Bay. Just stay cool and leave them alone. The one the lady threw out of the pool really should be called "a fish that looks like a shark". They don't really have much in the way of teeth. Glad she helped the poor thing out by chucking it back in the ocean.
Great whites, tiger sharks, bulls, bronze whalers however would be terrifying to encounter. We were swimming at a place called Hyams Beach in jervis Bay on the New South Wales south coast 15 years ago when a guy sauntered down from his beachfront house to tell us we should perhaps get out of the water as there were a few sharks about 50m offshore. That night on the news they reckon they were about 4m tiger sharks. That wasn't a good feeling.
