It was her fifth attempt, coming after four years of grueling training, precision planning and single-minded determination. Her face scorched and puffy from so many hours in the salt water, she leaned on one of her friends and said from the beach:

“I have three messages. One is we should never, ever give up. Two is you never are too old to chase your dreams. Three is it looks like a solitary sport, but it takes a team.”

Four YEARS of training. Fifth attempt. Wow!

Cuba-to-Florida swimmer says she is "through with the ocean"

Nyad credited a lack of box jellyfish, which she called the most deadly animals in the ocean, with allowing her to make it this time. She also wore a prosthetic mask to protect her from jellyfish, although it also allowed sea water into her mouth, creating sores and repeated vomiting during her swim.

http://in.reuters.com/article/2013/09/03/cuba-swim-diana-nyad-idINDEE9820EA20130903

I was wondering how she got through the jellyfish. They seem a worse threat than the sharks.

It doesn't look like it's that hard to swim from Cuba to Florida but actually it is damn near impossible.