A post on Nyad's blog says she's doing well and the crew is upbeat, though she expressed some fatigue during a pause to eat. Doctors examine her regularly and say "she's looking very good."
The 64-year-old is trying to become the first person to swim from Cuba to Florida without a shark cage.
It's Nyad's fourth attempt at the feat in the last three years. She also made an unsuccessful try with a cage in 1978.
If she's successful this time, she expects to take about 80 hours to reach the Florida Keys.
Nyad's handlers were giving fans status updates Sunday via social media.