Aug. 9, 2011 — -- Diana Nyad ended her second attempt at swimming from Cuba to the Florida Keys without a shark cage this morning, after lasting 29 hours in the ocean and being "surrounded by dolphins and a beautiful Caribbean sunset."
"We are sorry to report that Diana IS out of the water," read several posts from her Twitter account early this morning. "Realizing the conditions of 5 to 10 knot winds and less than ideal currents, Diana herself decided to end the swim."
The 61-year-old was blown 15 mph off course because of strong currents, according to Tweets on her page. One Tweet said that she was strong but disappointed.
"It's hard because I felt like I had it in me," several Tweets quoted her as saying. "It felt like this was my moment. I don't feel like a failure at all. But we needed a little more luck."
Nyad Was Going 'Strong' on First Day of Swim
A Tweet around 9 a.m. said that she had arrived in Key West and was awaiting customs. If Nyad had completed the swim, she would have broken her 1979 Bahamas-Florida record and become the first person to travel the strait without the aid of a shark cage.
An Australian swimmer completed the swim from Cuba to the Keys in 1997 but used a cage.
The long-distance swimmer was going "strong" Monday on the first day of what was expected to be a nearly 60-hour, 103-mile trek from Havana, Cuba, to Key West.
"If I go unconscious, that's one thing," one Tweet read at 12:13 p.m. ET Monday. "But no one is going to make me get out of the water; that will never happen."
At the Hemingway Marina in Havana Sunday, before starting the nearly journey, Nyad played "Reveille" on a bugle, thanked those who had come to cheer her on and then entered the water wearing a black swimsuit and blue swim cap.
"The adrenaline's flowing now," she said Sunday, looking out at the water. "I think this is my day."
Nyad told ABC News last month that an approaching birthday had sparked a desire to attempt a feat she had failed to complete when she was 28..
'One Day a Light Bulb Went Off'
"Turning 60, for the first time in my life, threw me into kind of an angst of worry and regrets over what I had not done through the course of my life," she told ABC News in July. "I decided to reach out for something that would take commitment, that would take everything in me. ... One day a light bulb went off."
In 1978, she attempted the crossing inside a steel shark cage for nearly 42 hours before having to stop because of sea currents.
In 1979, she set a world record for open-water swimming without a cage when she swam 102.5 miles from the Bahamas to Florida.
She then retired but said the unfinished Cuba swim stayed with her. As she neared 60, she said she considered returning to the sport of competitive endurance swimming.
"I started training and I found it was in my heart and it was in my body," she told The Associated Press.
Sharks' 'Dinner Bell'
"It's not a sensationalistic statement to say that the sharks that swim off here are very dangerous," Nyad told ABC News in July. "They're aggressive. They're curious. They for thousands of years have heard a fluttering on the surface to mean to them 'dinner bell.'"
Her team is using an electronic boom to surround Nyad with a current that will keep most sharks away.
"It's going to be a daunting task," Nyad said. "I feel confident and on the other hand I'll admit to you I feel afraid.
"When I tried to swim before in 1978, I was 28 years old. I didn't have as much fat on the body. I was faster in the water. On the other hand, at this age, I do feel a little more bullish," she said.
"I am much more in control of my emotions. I actually think I'm a better distance swimmer than I was in my 20s. In an emotional, mental sort of stance, I'm in an athletic prime even at just one month shy of 62," Nyad said.
She told ABC News that the message behind her swim was "to live your life big [and] burn the candle large.
"When I go to sleep at night, I say, 'How much more could I have put into this day?' Nothing. That's the way I want to live," she said.
The Associated Press contributed to this story.