A British-Australian dual citizen is trying to become the first woman to complete an unassisted swim 103 miles (166km) across the Straits of Florida without the aid of a shark cage.
Penny Palfrey, a 49-year-old mother of three and grandmother of two, said on Thursday that she was inspired to take on the shark-filled waters between Cuba and Florida last year when she flew from the Cayman Islands to Miami.
"I looked down, I could see this beautiful stretch of water, and wow!" she said. Ms Palfrey got home and immediately began researching currents in the strait and its water temperatures, which are similar to a 67-mile (108km) crossing she made last year between Little Cayman and Grand Cayman islands.
"By then I'm already hooked," Palfrey said.
Australian Susie Maroney made the Cuba-to-Florida crossing in 1997 at the age of 22, but she swam with a shark cage. American Diana Nyad made two cageless attempts last year on either side of her 62nd birthday, but they were cut short by asthma attacks and jellyfish stings. Ms Nyad plans to try again this summer.
Ms Palfrey will be swimming without a wetsuit or a cage and relying on "sharkshields" to keep the sharp-toothed predators at bay. The equipment generates an electrical field in the water that Ms Palfrey will not notice, but will annoy sensitive-snouted sharks enough so they stay away.
To guard against Portuguese man o' war stings, which sunk Ms Nyad's second and best attempt last summer, Ms Palfrey will don a Lycra bodysuit that covers her down to her wrists and ankles whenever it seems jellyfish may be a problem.
"It's porous and non-buoyant so it doesn't aid me as a swimmer," she said. "In fact it's harder to swim because it creates drag and there's a lot more seams, so there's some chafing issues."
Ms Palfrey had to call off two previous Hawaii swims due to Portuguese man o' war stings.
She will set out on Friday morning from the Hemingway Marina in Havana, and expects the swim to take between 40 and 50 hours. A 44ft (13m) catamaran dubbed the Sunluver will shadow her, carrying a support crew of navigators, kayakers, handlers, doctors, weather experts, and observers on hand to verify what would be a record swim.