Just 24hrs after Justine Barwick was mauled by a shark in the Whitsundays, there's a second victim.

A second person has been attacked by a shark at the same Queensland island where a Tasmanian mother was mauled less than 24 hours earlier.

A rescue helicopter flew to Cid Harbour in the Whitsunday Islands region around lunchtime on Thursday to retrieve a “another shark bite patient”, the RACQ CQ Rescue service tweeted, after reportedly being bitten on the leg.

On Wednesday evening, Justine Barwick, 46, was mauled while snorkelling nearby, and is lucky to be alive.

Ms Barwick, a mother of two, would likely have bled to death from a severe wound to her left thigh without the quick-thinking actions of people in nearby boats.

A rescue helicopter scrambled to the region was just 15 minutes away from the scene due to an earlier operation they’d been undertaking.

The hovering chopper drew the attention of John Hadok, an emergency department doctor from Mackay Base Hospital, who was sailing nearby and soon joined the effort to save Ms Barwick’s life.

Dr Hadok’s direction ensured correct first aid was given to Ms Barwick, allowing her to be safely winched into the helicopter.

RACQ CQ Rescue Helicopter crewman Ben McCauley said the doctor and others who gave first aid to Ms Barwick before she was winched aboard had likely saved her life.

“The original first aid was actually really well done,” Mr McCauley told reporters on Thursday.

A Tasmanian tourist is fighting for life after being attacked by a shark in the Whitsundays. #7News pic.twitter.com/hxm6TpisSy

— 7 News Melbourne (@7NewsMelbourne) September 20, 2018

“We actually didn’t have to do anything with the leg, it was pretty much tourniqueted up, bandaged up and bleeding had stopped. They’d done a really good job.”

Although he didn’t see the wound, Mr McCauley was told Ms Bariwck had “quite a big chunk of leg taken” and had suffered arterial bleeding.

She also suffered puncture wounds to her calf muscle.

The helicopter then stopped at Proserpine to refuel, allowing blood from a local hospital to be transfused and other medical treatment given.

Just after 8pm Ms Barwick arrived at Mackay Base Hospital where she remains in a critical condition on Thursday morning after overnight surgery.

Her husband Craig is at her bedside.

Ms Barwick works for non-profit Family Based Care in Burnie and had travelled to the Whitsundays on a holiday with her husband and friends.

Family Based Care chief executive Doug Doherty said Ms Barwick and Craig were regular visitors to the popular tourist destination in the heart of the Great Barrier Reef.

“It didn’t surprise me, because she is such a fighter, when she was being taken off the rescue helicopter and taken into hospital she was telling them what she was allergic too and still able to give directions,” Mr Doherty told AAP.

“That sounds like Justine to me.”