The 62-year-old marathon swimmer tweeted Thursday that she was aiming to begin another crossing of the Florida Straits on Sunday morning.

It will be Nyad's fourth attempt to swim from the Caribbean island just 90 miles off Key West, where she has spent weeks training and monitoring the weather for a favorable window.

Nyad first tried to make the crossing in 1978 as a 28-year-old. She swam inside a steel shark cage for about 42 hours before quitting.

She attempted the same swim without the shark cage twice in two months last summer. An asthma attack stopped her after 29 hours, and then jellyfish stings cut short the last attempt after 40 hours.