American endurance swimmer Diana Nyad made final preparations on Sunday to dive into the waters off Cuba in a bid to become the first person to swim the Florida Straits without the aid of a shark cage.

Tanned and freckled from long hours training in the open seas of the Caribbean, the 61-year-old Nyad expressed confidence before starting off.

She said the still air and flat water were perfect conditions for her attempt to make a 103-mile (166-kilometer), 60-hour swim from Havana to the Florida Keys.

"The adrenaline's flowing now," Nyad said at a jetty in Western Havana as she looked at the water. "... I don't believe much in destiny, but you have to take what you can get, and this is what I dreamed of: a silver platter."

She called the attempt a "symbolic moment" for increasing understanding between the United States and Cuba, two nations torn by five decades of animosity and mistrust. "I'm under no delusion that my swim is going to make any new political ramifications," she added. "But it is a human moment between the two countries."

Nyad began her meaningful swim Sunday night from the Marina Hemingway in Cuba and if everything goes as planned she will arrive in Florida in 60 hours.