Havana, Cuba (CNN) -- If Diana Nyad never realizes her dream of swimming the Florida straits, it won't be for lack of trying. The 64-year-old began her fifth and last bid to swim from Cuba to the United States on Saturday morning.
Previous attempts were thwarted by dehydration, ocean currents and excruciating jellyfish stings to her tongue.
"There's the fine line between seeing that things are bigger than you and letting your ego go," Nyad said at a news conference in Havana Friday. "And there's another edge over that fine line where you don't ever want to give up and I am still at that place!"
Were Nyad to swim the 103 miles from Havana to the Florida Keys, she would be the first person to do so without the benefits of a shark cage, flippers or wet suit.
And it would validate her attempts, which have spanned 35 years.
In 1997, Australian endurance swimmer Susie Maroney, then 22, completed the swim from within a shark cage.
Along with the protection the cage offers against toothy predators, swimmers say the cage provides a barrier against waves and other weather hazards.
Since Maroney's swim, some of the world's best endurance swimmers have tried to cross the straits of Florida without using a cage. All have been turned back.
But few have done so as persistently or as colorfully as Nyad.
The Key West, Florida, resident says she feels a special bond with Cubans and hopes her repeated efforts to swim between the two countries will help improve the still-tense relations between Havana and Washington.
Nyad often tried to communicate in rudimentary Spanish during the news conference Friday. She has said that during her long swims, she sings the Cuban ballad, "Guantanmera," to herself hundreds of times.
Cuban authorities said that after her latest attempt was announced in state media, they received a barrage of suggestions from across the island on how she could ward off the stinging jellyfish that ended previous attempts.
This time, Nyad said, she will wear surgical gloves and a specially designed prosthetic face mask to prevent the jellyfish from stinging her.
"It took us a year, we made mold after mold," Nyad said of the mask, adding it was the kind used to protect people who had suffered injuries to their faces.
"It's a two-edged sword for me. It's cumbersome, it's difficult to swim with, but it doesn't matter. I am safe. There's no other way."
Nyad will be accompanied by a 35-member crew aboard two sail boats. They will monitor her health, update her progress on social media and try to ward off sharks that might view her as a potential snack.
If all goes to plan, Nyad said, the swim will take her three days to finish.
CNN's Matt Sloane contributed to this report.