Stringer / Reuters

Penny Palfrey, an Australian-British swimmer starts her attempt to swim to Florida from Havana on Friday.

Updated at 6:40 p.m. ET: Strong currents early on Sunday defeated marathon swimmer Penny Palfrey in her attempt to complete a record-breaking 103-mile swim from Cuba to the United States without a shark cage.

Palfrey, a 49-year-old grandmother, was plucked from the waters of the Florida Straits at about midnight after setting out from Havana on Friday and swimming for more than 40 hours, her team told NBC News.

In a statement, her team said a strong southeast current that made it impossible for her to continue her swim and that she was on an escort boat being taken care off by her support crew.

Palfrey had already made it well past the halfway point across the dangerous body of water that separates communist Cuba from the United States.

"Penny has been 100 percent focused on this swim for a year, so she was quite a bit upset. There were of course some tears. She didn't know what was happening until we told her, so it took a few minutes while she took that in," her husband  Chris Palfrey said Sunday at a news conference in Key West, Fla. 

She was hospitalized Sunday, receiving IV drips and pain medication. Painful blisters and ulcers under her tongue made it difficult to talk. Her husband said it was too early to discuss the possibility of another attempt.

Her doctor said she was dehydrated and had low blood pressure, but remarked her blood work was fairly normal considering the swim.

"She was still strong, but 41 hours of continuous swimming ... she was physically exhausted," Chris Palfrey said. "It was really only her mental focus that was keeping her going. She was going really, really well but she only had a few more hours in her."

Palfrey, who was born in Britain but lives in Australia, had initially hoped to complete the crossing and arrive somewhere in southern Florida within 40 to 50 hours.

Her swim followed two unsuccessful attempts last year by American marathoner Diana Nyad, now 62, to cross the Florida Straits, which are known for tricky currents and unpredictable weather.

The swim was completed successfully by Australian swimmer Susan Maroney in May 1997, but unlike Nyad and Palfrey she used a shark cage. 

Reuters and The Associated Press contributed to this report.

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