U.S. endurance swimmer Diana Nyad appeared “to be gaining strength,” as she recovered from multiple Man o' War stings while making her second attempt in two months to swim from Havana, Cuba to the Florida Keys.

“Her rest times per hour are less and less,” according to a post on her blog.

The 62-year-old swimmer began her journey Friday evening from Havana's Hemingway Marina. The 166-kilometer swim is expected to take Nyad 60 hours to complete.

If successful, she will set a new record for open-water swimming without a shark cage. Nyad is protected in the shark-infested waters by an anti-shark device that uses an electrical current to shield her from predators.

She is accompanied by a small flotilla of watercraft manned by members of her team who pass her food, water, medicine and swimsuits.

Nyad insists her age was not a factor in her failed attempt in August. She said a crippling asthma attack forced her to retreat.

Nyad tried the same feat in 1978 when she was 28 years old, but ended it because of high winds and rough seas.

Australian swimmer Susan Maroney completed the swim in 1997 with the help of a shark cage. Maroney was 22 years old at the time.