Diana Nyad presses ahead in Cuba-Florida swim

American long-distance swimmer Diana Nyad stroked in the Florida Straits on Saturday, enduring stinging sea creatures as she pressed ahead in her latest bid to become the first person to swim from Cuba to Florida without a shark cage.

Nyad, 62, departed from the Cuban capital of Havana Friday evening on her quest to make the 103-mile crossing through shark-infested waters, a grueling swim expected to last a total of around 60 hours.

It is the second time in two months Nyad has attempted the swim. In August, she swam for 29 hours and about 50 miles before abandoning the effort. She said she suffered from asthma for 11 hours of the swim, which drained her strength.

IN PICTURES: Diana Nyad's swim from Cuba

She was about a third of the way to Florida by Saturday afternoon, moving through calm waters, according to her Twitter account.

At one point, a white tipped shark was spotted in her vicinity but eventually swam away as one of Nyad's safety divers approached it.

Nyad was swimming "stronger and stronger," a message said, after her pace slowed overnight when she suffered a series of stings from jellyfish-like Portuguese Man o'War and complained of breathing problems.

Stings on her arms, the side of her body and face forced her to tread water for more than an hour. She eventually changed her bathing suit and put on a shirt to cover herself.

"Her strokes are up to 50 per minute," another message posted on Saturday read. "She is eating pasta, gobbling bananas, bits of peanut butter sandwiches."

Under rules for the record swim attempt, Nyad can stop each hour to take liquids and high-energy food but cannot touch a specially equipped boat accompanying her. A team of about 30 people is keeping watch over her as she swims.

Even though she retired from competitive swimming years ago, Nyad has said she is trying the swim to help people her age and older realize they still can do many things. She also said the swim is an effort to improve U.S.-Cuba relations.

Nyad, who was raised in south Florida, first attempted the crossing from Cuba in 1978 when, at the age of 28, she was at the peak of her career as a marathon swimmer. Heavy seas forced her to give up before reaching Florida.

She has set several world records, including swimming around New York's Manhattan island in 1975 in less than eight hours and completing a 102.5-mile swim from Bimini in the Bahamas to Florida in 1979.

The Florida Straits crossing was successfully completed in May 1997 by Australian Susan Maroney, then 22, but she swam in a cage to protect her from sharks.

Nyad is being protected in the warm waters by an anti-shark device that uses a mild electrical current to shield her from the predators.

IN PICTURES: Diana Nyad's swim from Cuba