A second person has been attacked by a shark near Gracetown in Western Australia's South West, just hours after a man's legs were savaged in an incident which forced the Margaret River Pro surfing competition to be temporarily suspended.

In the latest attack, a Denmark man suffered minor injuries when he was bitten on the leg at the Lefthanders surf break, about 270 kilometres south of Perth, with the shark leaving significant bite marks on his surfboard.

Jason Longrass — who was surfing at a closed beach at the time — was treated by paramedics at the scene and said he was "very lucky".

Sorry, this video has expired Second man attacked by shark in WA's South West

The 41-year-old said he had been "having a ball" in the water prior to the shark attacking, with other surfers having cleared out of the water.

"[It was] just heading straight for me, beelining straight at me … and just nailed the board," he said.

"I knew straight away 'don't kick your legs, just swim'."

The second attack left significant shark bite marks in Jason Longrass's surfboard. ( ABC News: Gian de Poloni )

Earlier, another man was mauled about 2 kilometres away at Cobblestones surfing spot shortly before 8:00am, with fellow surfers helping him back to shore before applying tourniquets to his legs.

Sorry, this video has expired Shark attack victim flown to Royal Perth Hospital

Margaret River resident Alejandro Travaglini, 37, suffered significant leg injuries and was flown by a rescue helicopter to Royal Perth Hospital (RPH), where he is recovering from surgery in the trauma unit.

Alejandro Travaglini was attacked by a shark at Cobblestones surfing spot. ( Facebook: Alejandro Travaglini )

St John Ambulance said paramedics on the ground reported that first aid from his friends was crucial in the moments after the attack, as they used a leg rope to stem blood flow.

"I just want to thank all the legends who helped me up the beach," Mr Travaglini said in a short statement.

Victim body surfed to shore

Surf photographer Peter Jovic witnessed the attack on Mr Travaglini from the beach and said it reminded him of Mick Fanning's encounter with a shark at Jeffreys Bay.

"A shark popped up and pretty much ended up knocking a surfer from his board," he said.

"There was a lot more thrashing around. After that it was hard to see what was going on.

"[I] saw the guy who had been attacked get separated from the [surf] board and then start to paddle for an inside wave, which he managed to body surf all the way in.

"They got him to shore and started working on him to stem the bleeding."

Cobblestones surfing spot and beaches around Gracetown were closed after the first attack. ( ABC News: Gian de Poloni )

A 4-metre white shark was later spotted by the crew of Surf Live Saving WA's helicopter.

Shark launched out of the water: witness

Another witness, Brett Newland, said there were about five surfers in the area when "a big shark popped up in the water amongst them".

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"It swam under a couple of guys and came around and bit a third person," he said.

"We could see its fin, and then when it attacked the man we could see its tail splashing and saw it launch up out of the water at him.

"It was a large shark and from the way it was behaving, it would have been a white pointer.

"All the other surfers swam to him, helped him get away from his board and leg rope and helped him get on a wave, and luckily [he] caught a wave onto the reef."

Mr Newland said the man was conscious the whole time.

"The surfers that helped him in got tourniquets on his legs as soon as they got on the shallow reef, and then other people came down from the carpark and put him onto a surfboard and carried him up to the carpark," he said.

"He had cuts to both legs."

Mr Travaglini is a work crew member at the Margaret River Pro, and surfing officials said they were "devastated" by the attack.

"We're sending our thoughts and prayers to him and his family during this difficult time and we're working together to do everything we can to support him and his family moving forward," Surfing WA event director Justin Majeks said.

Whale carcass found nearby

Beaches in the Gracetown area were closed following the earlier attack, including North Point, Big Rock and Lefthanders, and a shark warning was issued for waters between Kilcarnup and North Point.

An alert was also issued about a whale carcass found at Lefthanders, with beach users warned the decomposing carcass could draw sharks close to shore.

A whale carcass washed up on the beach where the second attack took place. ( ABC News: Gian De Poloni )

Speaking after the second attack, Acting Fisheries Minister Roger Cook said authorities had taken every precaution possible.

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"Following the first incident authorities cleared beaches, erected beach closure signs, patrolled the area in boats and on foot to ensure the safety of other beach users," he said.

"Lefthanders beach was closed due to a whale carcass and a shark being sighted in the area.

"Signs had been erected at the beach, the helicopter was patrolling the beach and alerts had been issued on both SharkSmart.com.au and Surf Life Saving WA's Twitter.

"Unfortunately despite the warnings and beach closures being in place, a surfer has been bitten on the leg.

"This incident highlights the importance of heeding the beach closures and other warnings put in place by authorities."



Margaret River Pro suspended for an hour

The Margaret River Pro began last Friday and had been taking place in Gracetown over the weekend.

Hawaiian John John Florence won last year's Margaret River Pro and is back to defend his title. ( Source: WSL/Cestari )

Heats had returned to Main Break in Prevelly on Monday, but the competition was put on hold after the first attack at Cobblestones, about 15 kilometres away.

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Organisers decided to resume the competition about an hour later with "enhanced safety measures" after discussions with local authorities and surfers.

"We are confident, we wouldn't have resumed if we didn't feel that way," World Surf League (WSL) commissioner Kieren Perrow said.

"We've stepped up the presence of our jet-ski team, [our] water safety team.

"Typically we have three or four in the water dedicated to surfer safety and also to our shark safety protocol and we've stepped that up now, we've actually got seven in the line-up and we've increased our drone presence to two.

"Surfer safety is the foremost of our minds."

World champion's close call

Hawaiian pro surfer John John Florence had a close encounter while surfing in the region in the lead up to the competition.

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In video posted on social media, he recounted seeing something in the water and a splash before he raced back to shore.

He put a drone in the air and the video revealed two large sharks.

There have been 15 fatal shark attacks in WA since 2000, most recently when teenager Laeticia Brouwer was killed at an Esperance beach on Easter Monday a year ago.

The WA Government has since resisted pressure from the Federal Government to reintroduce shark drum lines and nets, saying they do not work.

A study released in February cast doubt on anecdotal claims of a jump in shark numbers off WA's coast, flaring renewed debate over whether the state needed to do more to protect swimmers.

Fisheries Minister Dave Kelly announced the State Government's shark mitigation plans last May, with the main feature a subsidy for shark deterrent devices.