A 38-year-old man was bodyboarding with a friend off Lighthouse Beach, about 400 kilometres (248 miles) north of Sydney, late Saturday afternoon when he was attacked and suffered "life-threatening injuries", New South Wales state police said.
He was treated at Port Macquarie Hospital for stomach and back wounds and was in a stable condition on Sunday morning, a hospital spokeswoman told AFP.
Beaches in the Port Macquarie and Hastings area remained closed today.
In the same area, a 32-year-old surfer's legs were mauled by a shark in early July and in February, a 41-year-old Japanese surfer died after his legs were torn off in an attack.
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The spate of attacks prompted authorities to boost the monitoring and tagging of sharks off the coast, with world-renowned experts temporarily based in the region to lead the project ahead of the busy summer season.
But the latest encounter was "quite unusual as there haven't been reports of shark activity in that (Port Macquarie) region for ages", a Surf Life Saving spokeswoman told AFP.
Experts say attacks by sharks are increasing as water sports become more popular.