Endurance swimmer Penny Palfrey has ended her effort to become the first woman to swim unassisted from Cuba to the Florida Keys, her support team said.
Ms Palfrey halted her effort early on Sunday about 26 miles south of Key West, roughly three-quarters of the way through, because of a strong ocean current, team member Andrea Woodburn said.
Ms Woodburn said she was in contact with Ms Palfrey's boat and was told the swimmer had gotten out of the water around about midnight.
Ms Woodburn said the British-born Australian is well, but gave no further details.
Ms Palfrey had been swimming steadily and reported no physical complaints other than jellyfish stings earlier in the day on the 100-mile-plus swim.
The Florida Straits are notorious for fickle ocean currents, including the powerful Gulf Stream.
Roughly 37.5 hours into the swim, the 49-year-old grandmother was 76 miles from her starting point at a marina in the Cuban capital Havana, according to her website's GPS tracking report.
At the time, she was positioned about 30 miles south, south-west of Key West.
Previously, Ms Palfrey's personal best was 67 miles when she swam between Little Cayman and Grand Cayman islands last year, according to Ms Woodburn.
The swimmer had reapplied sunscreen and grease to prevent chafing and said the water conditions had been excellent other than the extreme heat on the first two days of the swim. She spotted a few hammerhead sharks and dolphin pods on the way.
Crew members said she was in full control of the effort at the time, instructing team members who were accompanying her on kayaks and a catamaran.
Hours earlier, Ms Woodburn had said the conditions appeared ideal with bathwater-warm waters reported to be calm as the swimmer took aim for the Florida Keys. The 20-year veteran of distance swimming has been no stranger to jellyfish stings, which forced her to abort two past swims in Hawaii.
Ms Palfrey set off from Havana on Friday. A member of her crew was tweeting to fans, while a webpage updated her location every 10 minutes or so based on data from a GPS device worn by the swimmer.
The daunting effort has been commonly reported as a 103-mile swim, although the GPS coordinates suggest it is closer to 107 miles.
Multiple challenges loomed for Ms Palfrey on her second day in the water Saturday, including the prospect of physical and mental fatigue and fending off dehydration, hypothermia and potentially dangerous marine life.
At the rate she had been swimming, it had been estimated the crossing would have taken more than 56 hours to complete, slightly above her initial estimates. That would have put her on track for a Florida Keys' arrival sometime on Sunday if she had kept going.
Palfrey had been aiming for the record books to become the first woman to swim from Cuba to the Keys without the aid of a shark cage. Instead she had been relying on equipment that surrounded her with an electrical field to deter the predators. Her support team consisted of more than a dozen navigators, handlers and medical personnel escorting her on the 44ft catamaran Sealuver.
Ms Woodburn said that the swimmer was hydrated on the swim every half-hour with a liquid concoction containing electrolytes and carbohydrates.
Australian Susie Maroney made the crossing in 1997 at the age of 22, but with the protection of a shark cage. American Diana Nyad made two unsuccessful cageless attempts last year on either side of her 62nd birthday, but had to call them off due to a debilitating asthma attack and painful Portuguese man o' war stings. She has announced plans to try again this summer.
Ms Nyad's twitter feed displayed several messages focused on Ms Palfrey's effort.
"I'm sure our team will learn from her crossing," one tweet said. "Just as, I'm sure, Penny's team has learned from Diana's attempts."