The 46-year-old woman suffered severe leg and torso injuries when she was attacked in Cid Harbour, off Whitsunday Island, while swimming near a yacht late on Wednesday afternoon.

The woman, who had been staying at the Whitsundays on holiday, spent the night fighting for life in Mackay Base Hospital, where she remained on Thursday morning in critical condition.

RACQ CQ rescue crewman Ben McCauley said the shark had taken a "huge chunk" from the woman's inside leg and the quick actions of people onboard nearby vessels, including emergency department doctor John Hadok, saved her life.

Profusely bleeding, the woman was pulled from the water, transferred to a yacht and later moved to a dinghy to be winched up by a rescue helicopter dispatched from the coastal town of Proserpine.

“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," Mr McCauley said.

Queensland Ambulance Service manager of operations for Mackay Tracey Eastwick said the woman received immediate pain relief once onboard the helicopter.

"The patient was in a serious condition with a major haemorrhage and blood loss," she said.

"At the time she had altered levels of consciousness and was in a significant amount of pain."

She arrived at the Mackay hospital about 8pm, after the helicopter made a quick stop at Proserpine to pick up blood and to refuel.

“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,” Mr McCauley said.