The disappointment at giving up on her dream, though, was as raw as the welts left by the jellyfish-like creatures' long, stinging tentacles
"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 her medics said more man o'war stings might have killed her.
"It's such a bitter pill. I am so capable of that swim. That's the end, though" Nyad said.
Wearing a white bathrobe, the 62-year-old pushed up the sleeves to show a long, red, cross-shaped welt on her right forearm.
"Those damned jellyfish," she said.
Nyad said she had been in even better shape than when she attempted the same swim last month. She received oxygen and a steroid shot from her doctors while treading water as she recovered from the stings. 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.
The man o'war tentacles swept across her "like something out of a sci-fi movie," she said.
She kept swimming even as she felt paralysis stiffening her back, she said, because visions of Florida kept her going.
"I'm only human and I'm allowed to say I'm mad that it turned out this way, I'm very disappointed," she said.
"When you want something, you picture it, and I pictured seeing that Florida coast. The lights, the palm trees, I pictured it for so long. Go back to 1978, I pictured it a long time," Nyad continued. "It's hard to let go of, but I can, and I will. I'm not going to call you guys and say I'm doing it again. Mainly because of the way it ended."
Nyad ended her swim after swimming 130,098 strokes over 40 hours and 67 miles, 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 swimming.
Her team tentatively scheduled a press conference in Key West for Monday morning.
Nyad was making her second attempt in as many months at the Cuba-Florida crossing, a lifelong dream that she first tried as a 28-year-old back in 1978, when she swam inside a steel shark cage for about 42 hours before ending the attempt. 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.
Without a cage to protect her, 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.
"But never from that point on was I covering the miles," she said. 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 spent 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.
Nyad said her team told her, "These stings are cumulative. What makes you think you'll get through dusk again? They're everywhere."
Late Sunday morning, she heeded the warnings of experts who told her not to continue. She told The Associated Press earlier Sunday that she was in the best shape of her life but was blinded by the stings.
"You go into convulsions, your spine feels paralyzed. I've had kidney stones. Nothing compares to the pain," Nyad said, wearing loose bandages and rehydrating with water and juice on her boat. "It just took the life force out of me."
"I trained this hard for this big dream I had for so many years, and to think these stupid little Portuguese man o' war take it down," Nyad said.
Hours later, as Nyad tried to shrug off the possibility that someone else could complete the Cuba-to-Florida crossing, her friends tried to cheer her up.
Someone else could accomplish as much training and inspire as many people as Nyad has done over the last two years? "It will never happen!" they said.