The 55-year-old was pulled from the water with serious injuries and treated by police before paramedics arrived.
However, he died at the scene, according to police.
"That's pretty serious," said Daryl Roberson, a witness. "It could've been something like a criminal matter or something like that, and then to find out it's actually a shark attack."
Local media said the man was bitten on the upper thigh and hand. The species of the shark was unknown.
This marks the eighth person to die from a shark attack in Australia this year, the most since 1929.