Ambulance Queensland said: "Paramedics are treating a female child in a serious condition with a significant leg injury".
An RACQ CQ Rescue Helicopter spokeswoman earlier said the people the woman was with displayed heroism before the rescue crew arrived.
Melbourne girl Hannah Papps received a life-threatening wound to her leg on Thursday, a day after Tasmanian woman Justine Barwick, 46, was also bitten on her left thigh while snorkelling in the same harbour.
She was transported to Mackay Hospital by helicopter about 3.20pm and arrived about 4pm.
She was airlifted to hospital after being bitten on the leg while swimming in the same Whitsundays area in northeastern Australia, first responders said.
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.
Within hours of the second attack, Fisheries Minister Mark Furner announced he had activated special provisions to set up three drum lines in the area today.
Whitsunday Water Police confirmed they were not required to attend the incident and RACQ CQ Rescue confirmed they were attending an incident in that area, but details were not able to be provided at this stage.
Roseanne Barr says African-American comics called her after racist tweet
ABC reponded promptly; firing the comedian and cancelling her series , Roseanne . ABC had no comment on Barr's revelations when reached by TVLine.
She was treated by a doctor who was on a nearby boat, before being flown to hospital and undergoing surgery.
The area is a popular spot on the Great Barrier Reed for people who take sailing trips from Hamilton Island.
"I've dived with sharks and it's never been an issue".
"Nothing is more important than the protection of human life", he said.
"She is an avid snorkeller and enjoys these times away with family and friends", Family Based Care chief executive Douglass Doherty said.
"From what I'd heard on the radio, I had no idea it was a shark attack", he said.
Managing director Christophe Vanek says all its clients on the water have been warned to be vigilant and refrain from swimming in Cid Harbour and the broader Whitsundays for the foreseeable future.
Mrs Barwick was tonight transferred from Mackay to Brisbane by LifeFlight Air Ambulance jet for further treatment at the Royal Brisbane Hospital.