A 29-year-old man is being treated in hospital for a significant shark bite after being attacked while surfing in Falcon, south of Perth.
A surfer is fighting for his life after being mauled by a shark off a beach south of Perth.
It's believed 29-year-old Ben Gerring has lost a leg above the knee.
Mr Gerring's friend, Mandurah Boardriders Club president Brian Williams told the ABC he had just paddled further out into the ocean to catch a bigger wave when "all hell broke loose".
Fellow surfers pulled him from the water after he was attacked at Falcon Beach, a popular surfing spot just before 4pm on Tuesday.
"I paddled out to them, they needed a hand and that's when I saw this fellow, he was very pale, they had him propped up on a surfboard paddling in, there was about 100m to go so we got him all the way ashore and then applied CPR," Ian Barker told reporters.
Local reporter Nathan Hondros told Nine Mr Gerring was unconscious when he was brought ashore and had lost his leg from above the knee.
"It was just terrible to watch. There was a lot of distressed people on the beach."
Paramedics worked on the mine worker on the beach for about 20 minutes before he was transferred to a waiting ambulance and taken to Peel Health Campus 13km away.
He was later transferred 80km to the State Trauma Centre, accompanied by his mother.
Royal Perth Hospital's chief executive Dr Margaret Sturdy on Tuesday night described Mr Gerring's injury "as a significant shark bite and is getting a lot of medical input."
A Falcon Bay Beach Cafe worker told AAP that two men rushed in asking for ice, saying someone's leg had been bitten off.
The beach was closed from Falcon Bay to Westview Parade, including Yeedong Bay, after the attack.
Surf Life Saving WA tweeted earlier in the day that there was a public report of a 3.5-metre white shark sighted shortly before 8am (WST) at Pyramids Beach in nearby Dawesville, about 1.8km offshore.
The last shark attack in WA was in October, when there were two incidents that resulted in minor injuries.
A grey nurse shark was probably responsible for biting 18-year-old Eli Zawadzki on the foot while he was surfing at Pyramids Beach in Dawesville.
Later that same month, a man was bitten by a shark off WA's southern coast in Albany while diving from a boat and spearfishing, suffering minor injuries.