Diana Nyad spent two years training to make the dangerous swim from Cuba to Florida, knowing she would have to be mentally and physically strong to accomplish her dream. What she wasn't ready for were the stinging sea creatures that ultimately derailed her third record-setting try.

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"How naive of me not to think of these almost science-fiction, little animals in the water?" she said of the Portuguese man o' war, her face and lips still swollen as she took off her shirt Monday to show the long red welts visible against her tanned skin.

What hurt most, though, was the disappointment of having to give up.

"It's going to hurt my pride so bad when someone swims across that thing, and it wasn't me," the 62-year-old told friends who greeted her boat, Sunluver, at a Key West marina Sunday night.

Nyad quit Sunday morning after 40 hours swimming past sharks, barracudas and men o'war in the waters between Cuba and the Florida Keys. She could have fought through bad weather or medical problems, she said, but medics said more man o' war stings might have killed her.

Speaking with friends and reporters Monday, Nyad said she and her team were prepared to encounter man o' war and jellyfish, and they even discussed using nets or some kind of barrier to sweep them out of her path.

Man o' war first stung Nyad just two hours into her swim from Cuba. Her team tended to her for five hours until they reached international waters, and two doctors from the sports medicine center at the University of Miami's Miller School of Medicine met up with her to provide treatment.

Nyad said she kept swimming even as she felt paralysis stiffening her back, with visions of Florida to push her onward.

"After only two hours? I thought, 'This is going to be happening all the way across. I've got to deal with it. I'm not going to quit after two hours,'" she said Monday.

She suffered the next stings during the second night of her swim. She tried to fend off more stings by wearing long pants, a long-sleeved shirt and a full facial mask, with just her hands, feet and lips exposed.

Her lips were stung, and Nyad joked that her swollen mouth rivaled actress Angelina Jolie's famous pout.

Nyad ended her swim after swimming 130,098 strokes over 40 hours and 92 miles (148 kilometers), according to her website.

Throughout the swim, her team posted her progress on her blog, Facebook and Twitter. Dozens of well-wishers posted responses, calling Nyad an inspiration even after she quit.

Nyad was making her second attempt in as many months at the Cuba-Florida crossing, a lifelong dream she first tried as a 28-year-old back in 1978, when she swam inside a steel shark cage for about 42 hours. A cage-less attempt this past August fell short when, gasping for breath, Nyad threw in the towel after an 11-hour asthma attack she blamed on a bad reaction to a new medicine.

Australian swimmer Susie Maroney successfully swam from Cuba through the Straits and to the Keys in 1997, though she used a cage. Nyad was trying to become the first to finish it without a cage.

Nyad relied on equipment surrounding her with an electrical field that is harmless but deters most sharks. Her divers were there to gently discourage any who made it through. On Saturday, handlers spotted barracudas in the area, and she got a visit from a curious Oceanic white tipped shark that was shooed off by a support diver.

Not all encounters with marine life were unpleasant. Earlier in her journey, 10 pilot whales emerged in the distance ahead of the swimmer, according to one team tweet.

Nyad got out of the water for medical treatment after the second man o'war stings. Instead of trying to set a nonstop swimming record, she chose to continue trying to set a so-called "staged swim record," which would be valid so long as she was on the boat only for treatment and not to rest.

She said she defied her team's expectations by getting back in the water.

The decision to stop for good came as her team realized the time she spent swimming between rests dropped from 90 minutes to 40 minutes. That meant she would spend another two nights in the water, likely with more man o' war stings, before she reached her intended goal of Islamorada in the Middle Keys.

The University of Miami doctors said that the effects of the man o'war stings were cumulative, and Nyad was still hoarse and wheezing Monday. She said she was still in pain and shaky from her swim, but she expected to recover.

Nyad said she found solace knowing it wasn't a physical failing or bad weather that stopped her swim. She said she can give up her dream knowing she couldn't have done anything about the man o' war.

"I'm not strong enough to counteract that animal," Nyad said. "They're way beyond what I can do."