Diana Nyad adjusts her swimming cap before she attempts to swim to Florida from Havana, Cuba (AP/Ramon Espinosa)
Endurance athlete Diana Nyad has launched another bid to set an open-water record by swimming 103 miles from Havana, Cuba, to the Florida Keys without a protective shark cage.
Under a blazing afternoon sun at the Hemingway Marina in the Cuban capital, Ms Nyad adjusted her cap and goggles, pointed to the open water, blew a bugle and cried: "Adios amigos! Courage!" Then she leaped in feet first and stroked out toward her support boat.
Less than a week before her 63rd birthday the Los Angeles woman is attempting a feat that even the fittest of human beings would find daunting. It is a dream that has taken three years of marathon open-water training swims and multiple aborted attempts at the crossing.
In the summer of 2010, unfavourable weather kept her from even setting out. Last year, first a debilitating asthma attack and then painful, dangerous stings from box jellyfish forced her from the water on two separate attempts.
This time Ms Nyad is banking on a custom-made swimsuit to protect her from the jellyfish. It covers her head-to-toe with holes only for the eyes, nose and mouth.
It is non-buoyant but still creates drag in the water, so she hopes to don it only at night when jellyfish are more likely to rise to the surface.
"You have to learn from your mistakes. You don't do it the first time," she said at a news conference, deeply tanned with goggle-rings around her eyes. "We need some luck, but we do feel like we've solved all the problems."
On her second try last summer, Ms Nyad lasted 41 hours before calling it quits. She estimates it will take at least 60 hours to complete the swim to the Keys, and said the Straits of Florida were forecast to remain calm in the coming days.
Go-time had been planned for dawn today, US time, but shifting weather forecasts prompted a last-minute change. The water north of Havana was slightly choppy yesterday, but expected to quiet down.
In June Australian endurance swimmer Penny Palfrey made it 79 miles of the way before throwing in the towel in the face of strong currents.