Woman, 62, hopes to Los Angeles to break her own world record for swimming in open water without a shark cage, set it in 1979 when the powerful of the Bahamas to Florida.
The failure of past attempts at crossing Cuba to Florida August 9 due to an asthma attack that forced her paralyzed from the water gasping for air after 29 hours.
Nyad insisted that this time was willing to brave the choppy seas, and schools of jellyfish and the limits of exhaustion of rights to achieve her dream of a lifetime.
With dark, about an hour and a half in the pool, and sent a team Nyad Twitter message that it "remains strong."
Just before it started from the Marina Hemingway Friday evening, aides grease smeared on her shoulders to prevent anger during the 60-hour trip had been planned. She pumped her fists in the air and support the team blew horns and cheered from the waiting boats.
"I feel good, and I feel very good," said Nyad. "But as you know, it really does not matter how I feel now."
Recognized as a bit quieter than the last time she left the marina itself.
"I am not conceited than ever before, but after it has been through this now, and was deeply disappointed emotionally, and I do not want to take anything for granted," said Nyad.
"It's not that I do not want to enjoy every moment, and taste, but they do not do any good to act like" Oh I've got this in the bag, and this is not going to be easy. "
Before jumping in the same weight Nyad tables and put 146 pounds. She said she expects to lose about 15 million pounds during the course of the journey. He called to schedule to get to Florida early Monday morning.
She hoped to take advantage of what he described as the "magic window" of the calm sea and favorable weather is expected to continue through the weekend.
The Nyad last month after a previous failed attempt, he promised there would be no repeat, but joked earlier on Friday that no one should believe them.
"Do not listen to the athletes when they say it's over," she said.
Nyad likened itself to the former boxer Roberto Duran, who retired in 1998 at the age of only 47 to re-enter the ring a year later.
He denied Nyad problems in a last attempt have anything to do with her age, saying it can be fought through waves of volatile and "painful" shoulder pain. But it did not expect 11 hours of an asthma attack blamed on a reaction to the medication she has never used before. She and asthma and had a through beating on the water "like a fish floundering and dying."
Even with those problems, and she made it about 50 miles (80 km) in the long (166 km) 103 miles.
In the weeks that followed concluded that the assassination attempt was not so much a failure as a rehearsal, a part unplanned, but necessary for the training system, which included a set of shorter swim.
"The asthma took me down, but enough of the ironic, that 29 hours was like a swimming pool training very, very expensive," said Nyad, estimated earlier this year that it took half a million dollars to get her first attempt.
"I'm in a better position than ever before, and I am more prepared than ever before," she added.
Without a cage to protect it, Nyad is to rely on special equipment which is surrounded by an electric current with almost imperceptible to humans, but strong enough to keep most of the sharks in the Gulf. Kayakers also along with the rowing gently away any urge to make it through.
For the length of the crossing, Nyad will not be allowed to touch the boat if the record is a count. Can not physically help her team to pass another of her food, medicine, and a new swimsuit and so on.
She said it was an attempt to maintain their energy by eating sandwiches and pastries such as peanut butter, she sang the Beatles and Bob Dylan and Janis Joplin songs in her head to keep her mind occupied, especially during the night.
"I was not at all - it's a basic rule - I never look for it very frustrating to see on the horizon with no lights, nothing, and I did not ask the coach and I am here in a boat what is the time, or" Are we almost there. So far? "Said Nyad." They're going to tell me when we're about 10 hours away. "
Nyad first tried to cross the Straits of Florida where he appeared 28 years in 1978, when he swam into a steel cage shark for a few hours before it ends about 42 attempt.
Now 62, after celebrating her birthday on August 22, she has said she hopes to inspire people to live an active life in the golden years. It also called for a symbolic swimming to increase understanding between the United States and Cuba, two countries torn apart by five decades of hostility and mistrust.
Marina made Brigadier Jose Miguel Diaz Escrich, described as Nyad dear friend, who helped with logistics in Cuba, and has honorary membership of the marina earlier Friday and called swimming, "Friendship Bridge" between the two countries.
"He's trying to have succeeded already," said Escrich in the promotion, citing the poet and Cuban independence hero Jose Marti.
A team Nyad hopes to try swimming in 2010, but was unable to make the necessary arrangements in time. This year has been very supportive of Cuban officials in arranging logistics and news media coverage.
"We're ready for everything that could possibly come our way this time," said Nyad ", and I just can not imagine any other ending of the ending that I want, which is to get all the way through."