Australian Chloe McCardel will battle exposure, swift sea currents, jellyfish, sharks and her own physical limits when she attempts a record swim from Cuba to Florida this week.
The 29-year-old, who is bidding to become the first person to make the 100-mile Straits of Florida crossing without the protection of a shark cage, said that the challenge has great allure for top athletes.
"At the moment it's the most high-profile marathon long-distance swim, and swimmers really want to come here and be the first. It's very important; it's like winning a gold medal."
Experts and doctors will accompany McCardel on her swim, which should last about 55-65 hours if she makes it all the way.
Every half-hour or so she plans to pause to eat and down a half-litre of energy drink to stay hydrated.
Meanwhile, special equipment will include an electromagnetic field in the water around her that is designed to keep sharks at bay.
McCardel has been swimming since childhood and also competed in triathlons. She has made six solo crossings of the English Channel, two double-crossings in 2010 and 2012 and won the 28.5-mile Manhattan Island Marathon Swim in 2010.
She has been training for the Havana-Key West swim for the last six months, averaging about 37-56 miles a week.
McCardel said a key to fighting through long-distance swims is focusing on her stroke in an almost meditative way, and remembering those who have supported her back home and around the world.
"I need to think very positive, uplifting thoughts," she said. "I'm going to be imagining the finish, imagining how amazing and happy I'll be walking to shore, visualize the people being around ... really being in the moment. So that's a positive thing that I use as a goal to work towards."
McCardel is also swimming to raise money to support cancer research, people who suffer from the disease and their families, and promoting the idea that an active, healthy life can help keep it at bay.
She's dedicating the swim in part to her mother, a breast cancer survivor. "But also other people out there who have cancer," she said, "or have relatives or friends going through that process, or who've passed away from that disease."