KEY WEST, Fla. -- A 49-year-old grandmother and veteran endurance swimmer scuttled her quest early Sunday to become the first woman to swim unaided from Cuba to the Florida Keys, unable to close the gap on the last 26 miles of a more than 100-mile ocean odyssey.

Penny Palfrey had fended off painful jellyfish stings while keeping an eye on hammerhead sharks as she attempted the crossing without a shark cage. But her support team said the tricky currents of the Florida Straits proved to be her biggest obstacle, thwarting her achingly close to her goal.

All told, the British-born Australian athlete had been swimming nearly 41 hours since plunging into balmy waters near Havana, Cuba, on Friday to start out. She was about three-quarters of the way into her swim when she gave up the effort about midnight, just 26 miles south of Florida's Key West.

PHOTOS FROM PALFREY'S SWIM (Story continues below):

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  • Penny Palfrey, Chris Palfrey

    British-Australian swimmer Penny Palfrey and her husband Chris rub creme on her body in preparation for her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators. (AP Photo/Ramon Espinosa)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey smiles as she is flashed a thumbs up at the start of her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators. (AP Photo/Ramon Espinosa)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey jumps into the water to begin her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators. (AP Photo/Franklin Reyes)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey, begins her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators.(AP Photo/Ramon Espinosa)(AP Photo/Franklin Reyes)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey begins her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators. (AP Photo/Franklin Reyes)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey begins her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators. (AP Photo/Franklin Reyes)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey, adjusts her goggles at the start of her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators.(AP Photo/Ramon Espinosa)

  • Penny Palfrey

    British-Australian swimmer Penny Palfrey, smiles before geginning her bid to complete a record swim from Cuba to Florida, in Havana, Cuba, Friday, June 29, 2012. Palfrey aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she's relying on equipment that surrounds her with an electrical field to deter the predators.(AP Photo/Ramon Espinosa)

Her crew tweeted few details early Sunday of the end of her quest but said: "Penny Palfrey had to be pulled out of the water ... due to a strong southeast current that made it impossible for her to continue her swim. Penny is presently on her escort boat being taken care of by her crew."

"She is fine," Andrea Woodburn, one of the team members, confirmed by telephone from Key West.

Wooburn said early Sunday that she had been in contact with the escort vessel during the night and it was unclear where it would head next. She had no immediate details on Palfrey's physical condition or the currents she had encountered.

The Straits are notorious for their fickle ocean currents, including the powerful Gulf Stream. But whether she encountered problems with the Gulf Stream or a side eddy of that current or some other were not immediately apparent.

At last report about 10 p.m. EDT Saturday (0200 GMT Sunday) - roughly 39 hours into the swim - Palfrey was 79 miles (127.13 kilometers) from her starting point at a marina in the Cuban capital, according to an online GPS tracking report. She was positioned about 28 miles (45.06 kilometers) south, southwest of Key West.

But two hours after the 10 p.m. Saturday report, it appeared based on GPS data that she had made difficult headway before scrapping her effort. GPS data released online suggested she had been averaging as much as 3 mph while swimming at her strongest Saturday, before her speed then slowed to 2 mph and less after sundown.

Earlier Saturday, however, Palfrey's crew reported she had been swimming steady and strong in calm, tepid ocean waters that were virtually ideal for the attempt at the record books. She also had reported no physical complaints other than the jellyfish stings more than halfway into the swim.

Palfrey had sought 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 44-foot (13-meter) catamaran Sealuver.

She said she spotted a few hammerhead sharks and her crew said they delighted in dolphin pods spotted on the ocean.

After Palfrey set off Friday from Cuba, a member of her crew was tweeting to fans regularly and her webpage was updated with her location every 10 minutes or so based on data from a GPS device she wore. The daunting effort has been commonly reported as a 103-mile (166-kilometer) swim, however the GPS coordinates suggest it is more like 107 miles (172 kilometer).

She faced numerous challenges, 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 - with arrival sometime Sunday in the Keys if she had kept going.

Australian Susie Maroney made the crossing in 1997 at age 22, but with 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.

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