TODD Robinson says he didn't believe "all the hype" about sharks until he almost became the latest victim of an attack while diving for crayfish off Hillarys yesterday morning.

The Padbury man was diving near Little Island, about 2km offshore, when he reported seeing a "large dark shape".

A friend pulled him from the water and Mr Robinson later discovered bite marks on his swim fins.

"I said, 'Pull me out, mate, there's a shark'," he said.

He reckoned the creature was up to 4m long. "My boat is 2m wide by 4m long and it was as big as that," he told Channel 7 last night.

"My main thing was just looking at my mate and the fear in his eyes looking back at me as I was trying to get back in the boat and I imagine the fear in my eyes looking back at him.

"There are a lot more sharks out there than people have made out there is.

"I didn't believe all the hype, until now."

On their way back to shore the two men flagged down a volunteer rescue team, who raised the alarm with Water Police about 11am. Fisheries spokeswoman Lisa Clack said the fins had marks consistent with a shark bite, but they could not rule out an attack from a seal or sea lion.

"We're unable to confirm it is a shark bite," she said.

"There are some marks on the fins that are consistent with a shark bite, but other marks you would expect to see are missing."

The attack came a few hours after the Department of Fisheries detected a tagged white shark at Scarborough, which forced the closure of beaches between Swanbourne and Scarborough.

But Ms Clack said it was unlikely the same shark was responsible for the attack because none of the three acoustic receivers near Little Island detected a shark yesterday.

The attack comes just two weeks after Greg Pickering was bitten near Esperance while diving for abalone.

Recent shark attacks in Perth

WA's shark attack victims

Meanwhile, a diver in the South-West reported being "circled" by a shark at Meelup Beach, near Dunsborough. He reported the incident to Water Police just after 3.30pm.

Fisheries South-West manager Kevin Donohue said the man was spearfishing when he was approached by a white shark estimated to be between 3.5m and 4m long.

"It circled him and approached him directly so he poked it with his speargun," Mr Donohue said.

"The shark moved to the fish on his float line so he dropped the line and the shark swam off with the fish."

Fisheries advise a 4m + shark has bitten off scuba divers fins. just off Little Island Hillarys. Diver is ok. Reported at 10:55am today.

UPDATE: Beach-goers from the Marmion Anglers Club to Mullaloo beach are currently being warned by lifesavers to take extra care.

Westpac Helicopter is on scene at Little Island.

Westpac Helicoper has returned to base and was unable to locate shark. Beachgoers advised to take additional caution in the Hillarys area.

For shark alerts visit twitter.com/SLSWA