i have met one bloke who says he lost a chunk out of his hamstring from a bull shark around nsw, i think happened during a capsize. it was always funny sailing in port lincoln, you would sail past a couple of guys trying to right their 14 foot skiff, and you would scream and point at the water, the boat would come up in a hell of a hurry. hee hee sorry fritz!!!! i was only joking!!
never actually saw one while sailing " off the beach" stuff at lincoln. seen plenty off henley though. sailing a nacra 5.2 with joel hunt and had a white on the surface swim between the hulls, he/she was longer than the 5.2 , as you said, messy undies, especially when they roll over on their side and eyeball you.