A young woman, Elyse Frankcom, was bitten by a 3m shark, and thanks to one of her client's intervention, probably escaped more serious injuries. Apparently this client pulled on the tail of the shark as it bit on to Frankcom in the thighs, causing it to let go and retreat. They were part of a group of snorklers who were swimming with dolphins when this incident occurred.
Dolphin pods with young have been known to have sharks tailing them, either waiting to take a young one or scavenge on their food. Pilot whales also have sharks like oceanic whitetips following them around. I'm not sure what kind of visibility they had on that day but an attack like this, where a shark goes after a big group of snorkelers, would indicate the visibility wasn't all that great.
Elyse escaped a possible life threatening incident and the man who saved her did not acknowledge the press and remains anonymous! A true hero!