HAVANA, Cuba -

Third time's a charm?

Endurance athlete Diana Nyad has launched another bid to set an open-water record by swimming 103 miles between Havana and the Florida Keys without a protective shark cage.

The American is attempting a feat that would daunt even the fittest of human beings less than a week before she turns 63 years old.

It's also a feat that she failed to accomplish twice last summer, due to an asthma attack and dangerous jellyfish stings.

Nyad set out from the Hemingway Marina in the Cuban capital Saturday afternoon.

She pointed to the open water, blew a bugle and cried "Courage!" before leaping in feet-first and stroking out toward her support boat.

She expects to take at least 60 hours to complete the swim.