Australian Chloe McCardel is recovering Thursday in Florida from jellyfish stings that forced her to abandon her attempt to become the first person to swim from Havana to Key West without a shark cage.

"Chloe McCardel and her team have safely returned to Key West in Florida after her attempt to swim from Cuba to the U.S. was ended by severe and debilitating jellyfish stings," according to a statement Thursday on the swimmer's Facebook page.

The 29-year-old was trying to set a new world record for a solo unassisted ocean swim, but had to end the attempt after covering 19 kilometers (12 miles) in 11 hours.

McCardel began her endurance swim from the Ernest Hemingway International Nautical Club, located just west of the Cuban capital, wearing a normal swimming suit, goggles, swim cap and a cream to protect her skin.

The Australian, whose goal was to complete the 166-kilometer (103-mile) journey in roughly 60 hours, knew beforehand she could encounter obstacles such as jellyfish stings, strong currents or even the possible appearance of a shark.

"After swimming non-stop for 11 hours, Chloe was stung around the neck, arms, back, mouth, and tongue," according to the note on McCardel's Facebook page, which was filled with messages of support.

"Concern was raised regarding the swelling in the area, affecting Chloe's ability to breathe efficiently. The decision was made to end the attempt."

McCardel's 32-person support crew, which included doctors and meteorologists, accompanied her aboard several boats after she jumped into the warm waters off Cuba on Wednesday.

The Australian was trying to break the record for a solo unassisted ocean swim that was set by Australian-British woman Penny Palfrey, who covered the 108-kilometer (67-mile) distance from Little Cayman Island to Grand Cayman Island in 2011.

Prior to McCardel, the last person to attempt to cross the Straits of Florida unassisted was American sexagenarian Diana Nyad, who set off from the same spot in Havana in August 2012 but had to abandon the swim due to severe jellyfish stings and an unexpected storm after completing more than 60 percent of the journey.

Australian Susan Maroney completed the Straits of Florida crossing in May 1997, but did so while enclosed in a cage to protect herself from potential shark attacks. EFE