Australian endurance swimmer Chloe McCardel aborted her attempted swim from Cuba to Florida after 11 hours in the water when she suffered "debilitating" jellyfish stings.
McCardel, 28, was attempting to make the nearly 100-mile swim in 60 hours through the shark-infested waters without a shark cage, but had to end her trek late Wednesday night.
"So the word is that Chloe has suffered a 'debilitating' severe jellyfish sting that made it impossible to continue," McCardel's Facebook page said in a statement. "She and the team are now heading towards Key West. Thanks everyone for all your support and best wishes."
Bob Olin, skipper of the primary support boat, the Sunluver, said McCardel had suffered multiple stings.
"She got nailed all over her body: back, legs and arms. Nailed multiple times, all at the same time," he told The Associated Press by satellite phone.
Olin said the team tried to treat her wounds while she remained in the water, but had to take her on board a boat because she was suffering "excruciating pain."
A team of 32, including weather experts and doctors, were traveling on a boat next to McCardel, who vowed she wouldn't leave the water.
"I will not wear a wet suit. I will not hold onto anything. I will not get on the boat at anytime," she said shortly before beginning her trek Wednesday morning in Havana, Cuba.
A smiling, upbeat McCardel had arrived in a pink 1950s Chevy convertible at a rocky jetty in western Havana.
"I'm pretty excited, I'm trying to stay calm and relaxed and just think about the finish," she said.
The only assistance McCardel received was liquid meals given to her in a bottle every half hour by a teammate who was paddling next to her.
McCardel's journey was inspired, in part, by U.S. swimmer Diana Nyad, who has tried the same swim four times but has never been able to finish. Her latest attempt came last year at the age of 62. Nyad's journey was thwarted by jellyfish stings and strong currents.
"It's a tough night for Chloe McCardel, a superior swimmer and an exemplary spirit," Nyad tweeted.
Australian Susie Maroney successfully made the swim in 1997, although she did it with the benefit of a shark cage.
The Associated Press contributed to this report.