A Tasmanian tourist is lucky to be alive after a shark attack in the Whitsundays left her with horrific injuries.

The 46-year-old woman was swimming from a charter yacht in Cid Harbour at Whitsunday Island when she was bitten on the upper right leg about 5:00pm on Wednesday.

The woman was pulled out of the water onto a nearby yacht, which happened to have a doctor on board.

Justine Barwick, 46, from Burnie in Tasmania, and who works in aged care for Tasmania Family Based Care, was mauled by a shark while on holiday in north Queensland in September 2018. ( Supplied: Tasmania Family Based Care )

She was then placed inside a dinghy and winched up to the helicopter.

Queensland Ambulance Service (QAS) Mackay manager of operations Tracey Eastwick said the woman suffered a significant shark bite to her right thigh and had a smaller wound to her lower right leg.

"Fortunately there was a doctor on scene, Dr John Hadok, who is an emergency department doctor," she said.

"He was able to assist with immediate treatment of the patient and to stabilise the serious haemorrhage that she had."

Ms Eastwick said the woman was given "immediate pain relief and fluid management" once onboard the rescue helicopter.

"The patient was in a serious condition with major haemorrhage and blood loss and at that time she had altered levels on consciousness and was in a significant amount of pain," she said.

The woman was airlifted by rescue helicopter to Mackay Base Hospital, where she underwent surgery on Wednesday night.

Her condition was described as "critical" by a hospital spokeswoman.

A Tasmanian woman is stretchered into Mackay Hospital after a shark attack in the Whitsundays left her with horrific injuries. ( ABC News )

Rescue helicopter lucky to be close by

RACQ CQ Rescue crewman Ben McCauley said the rescue helicopter had been on a beacon search at the nearby town of Proserpine when it was called to the shark attack.

Mr McCauley said the woman had to be pulled from the water and lost a vast amount of blood.

"The shark had taken a huge chunk out of her inside leg and she was bleeding out," Mr McCauley said.

"The people on scene who got her aboard that yacht and quickly packed the gaping wound to help stem the haemorrhaging undoubtedly saved her life.

"Given how serious her injuries were and how far from shore and from medical help they were, without the rescue helicopter I don't think she would have made it back to the mainland alive.

"She really was incredibly lucky."

Emergency doctor John Hadok from Mackay Base Hospital was nearby and able to provide first aid to the woman. ( Supplied: Facebook )

Two visiting fishermen from Canberra and Lake Macquarie have been out on the water in the Whitsundays all week and said they have seen plenty of sharks.

"We've caught a few, about four so far, all over a metre long, we were just doing normal fishing and that's all we can catch," Darren Chapman said.

"They're definitely out there, more than people think, you don't know because people don't get bitten very often."

Cid Harbour is a popular spot for bareboat charters and private boats off Whitsunday Island, which is about 100 kilometres north of Mackay.

Queensland Premier Annastacia Palaszczuk thanked the rescue personnel who attended the incident.

"Like so many Queenslanders I was horrified to hear details last night of a shark attack on a Tasmanian tourist at Cid Harbour on Whitsunday Harbour," she said.

"Can I extend my thanks to the calm professionalism once again displayed by our police, paramedics and other rescue services in dealing with this incident.

"On behalf of the house, can I offer our best wishes and prayers for a speedy recovery to the woman involved."

It's believed the woman was on board a Queensland Yacht Charters boat at the time of the incident.

The company said the incident was quite traumatic for all involved but said they were thinking of the woman and the family at this time.