Senior US distance swimmer Diana Nyad launched her second attempt in as many months Friday to swim 160 kilometers (100 miles) of sea from Cuba to Florida.

Nyad began her journey at 6:04 pm (2204 GMT) from the Ernest Hemingway International Nautical Club, just west of Havana.

It was the 62-year-old's third try to traverse the waters, after failed bids in 1978 and in August, when shoulder pain, asthma and ocean swells prevented her from fulfilling a quest to swim across the treacherous Florida Straits from Havana to Key West, Florida.

"Now I'm in better condition than I was in August, and I'm as prepared as ever... to achieve this dream," Nyad told reporters earlier in Spanish.

If Nyad succeeds, she will be the first person to swim the stretch of ocean without a shark cage.

Australian swimmer Susie Maroney, at 22, became the first person to swim from Cuba to the United States in 1997, though she used a shark cage.

Nyad said she was ready for the 60-plus hour ordeal.

"If I could swim to the half-way point dealing with asthma, I know today that I can complete it," she said, referring to her August attempt.

Nyad tried to swim across the shark-infested straights in 1978, but gave up after 42 hours in the water due to bad weather.

"This moment is about much more than sports for me," she said, expressing hope for better ties between communist Cuba and the United States, two former Cold War foes.

The swimmer set an open sea record by swimming from the Bahamas to the Florida Keys -- a journey that is the same distance as the Cuba-Florida swim, but a feat she described as much less dangerous.

And she clinched a record for circling the island of Manhattan at the age of 50, clocking in at seven hours and 57 minutes.

As in her previous journey, five yachts and four kayaks will accompany her, along with a 45-person support team, including trained shark divers and electronic devices designed to repel the predators.