A man has been treated for shock after has was knocked off his boogie board by a great white shark in Western Australia’s south.

The man was less than 50 metres offshore at Casuarina Point in Bunbury on Sunday morning when the big shark bumped his board, with photos provided by WA Police showing substantial damage.

A Surf Life Saving WA spokesman said the man was shaken by the close encounter but managed to make his way back to shore and raise the alarm.

He was treated for shock but was not injured and did not need to be taken to hospital, a St John Ambulance spokesman said.

A City of Bunbury ranger said the man left his boogie board behind and it was retrieved by the local marine rescue group.

The ranger said the shark appeared to be 3.5m long.

“He took off pretty quickly – probably to buy himself a Lotto ticket,” he told AAP.

“I’m sure it was pretty scary.”

The ranger described the cool and overcast conditions as “sharky weather”.

He said a salmon migration that had been going for several weeks was continuing and usually attracted more sharks.

“But I think it was random … in the wrong spot at the wrong time.”

Casuarina Point and the adjacent beach known as Hungry Hollow have been closed for the day.