Havana, Cuba (CNN) -- An Australian woman is planning to dive into the ocean off Havana on Friday in her bid to become the first person to swim across the Florida Straits without a shark cage or swim aids such as flippers or a wetsuit.
If successful, Penny Palfrey, 49, would surpass her own record that she set in 2011 for the longest unassisted swim. Palfrey swam more than 67 miles from Little Grand Cayman island to Big Grand Cayman island.
Her swim to the Florida Keys will cover a much great section of water, much of it shark-infested.
"She will swim continuously 103 miles or 166 kilometers under standard open-water swimming rules; that means no wetsuit, no shark cage," her husband, Chris Palfrey, said Thursday when the couple spoke to reporters.
"There have been other attempts, but no one has completed the swim under these rules. We expect the team to take 40 to 50 hours," he said.
In 1997, fellow Australian swimmer Susie Maroney completed a similar swim but from inside a shark cage.
In 2011, long-distance swimmer Diana Nyad twice tried and failed to complete the same journey. Nyad was waylaid by asthma attacks and stings from Portuguese man-of-war jellyfish.
A lycra suit will provide her some protection from jellyfish, Palfrey said, and long cables called "shark shields" will be strung from the kayaks and boats around her to ward off larger predators.
"They emit an electric field through the water, which when a shark comes within 5 meters, it picks up the sensors on the snout, but they don't like it. They swim away," Palfrey said.
Palfrey, who is a mother of three and grandmother of two, said she hopes that swimming in the wake of Tropical Storm Debby will provide her with calm seas.
A crew of 15, including medical personnel and meteorologists, will shadow her from boats and kayaks. She will try to stay nourished and hydrated by consuming a carbohydrate-rich drink every 30 minutes, she said.
Even though she has completed long-distance swims of the English Channel and a round-trip crossing of the Strait of Gibraltar, the waters between Cuba and the United States present their own hazards, she said.
"Each swim comes with its own challenges. This is a really big challenge; 103 miles is further than I have ever swum before," Palfrey said. "I expect it to be very challenging, but I am very excited."