American Diana Nyad is moving toward the halfway point Sunday in her third attempt at swimming from Havana, Cuba to the Florida Keys .

Late Saturday, Nyad was treated by doctors aboard a support vessel after being stung a second time by Portuguese Man o' War jellyfish.

Her support team says she is now attempting a record “stage swim rather than a non stop swim.”

Nyad hopes to finish the 166-kilometer swim on Monday morning – about 60 hours after she started. If successful, she will set a new record for open-water swimming without a shark cage.

Nyad's website says she is protected from sharks by three divers and an electrical current.

The 62-year-old swimmer began her journey Friday evening from Havana's Hemingway Marina.

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

Nyad insists her age was not a factor in a failed attempt in August. She said an 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.