This isn't really a surprising event.
The guy is an abalone diver, operating in a deepwater area with a seagrass bottom, seal colonies nearby, and he was digging around in the kelp. The shark was only a little juvenile 3 metre great white, and just chewed on him, and then spat him out when all it got was a lead vest and a poke in the eye. It would have mistaken him for a seal in the kelp, but then realised its mistake.
Thankfully everyone seems to have avoided the usual aggressive reaction.
Still, it would have been pretty nasty!