An American woman is hoping to become the first person to swim from the Caribbean island of Cuba to Florida in America - without a shark cage.
61-year-old Diana Nyad is swimming 103 miles through shark-infested waters, but she's got a team of helpers to protect her from any snapping jaws.
Back in the 1970s, Diana was one of the world's greatest long-distance swimmers.
Now she's back in the water, hoping to swim into the record books.
Watch Ricky's report.