Endurance swimmer Nyad to attempt Cuba-Florida crossing again HAVANA (Reuters) - U.S. endurance swimmer Diana Nyad will attempt to swim from Cuba to Florida this weekend, better prepared for the sharks, venomous jellyfish and powerful Gulf Stream currents that foiled her four previous attempts at the 103-mile (166-km) crossing. If she succeeds, Nyad, 64, would become the world record holder for the longest unassisted open ocean swim, meaning no shark cage protected her during the swim, which is expected to take more than 60 hours. Equipment emitting a mild electric current in the water should keep sharks at bay. Nyad said on Friday that a protective silicone mask would better protect her from the poisonous jellyfish that forced her to end one of two attempted crossings last year. She said the custom-made mask slows her and makes it more difficult to breathe, so it may take up to 80 hours to complete the swim. But it should help shield her from paralyzing stings and prevent toxins - including those from potentially deadly box jellyfish - from building up to dangerous levels in her system as happened last year. Lightning and the mighty ocean current that flows west to east through the Florida Straits were among other factors that cut short the two attempts Nyad made in 2012. This time, though, she said she was determined to make it and suggested, when she sets off as early as Saturday, that it would be her last try. It is my dream. A dream is life. I want it, I want to arrive at the end," Nyad told reporters at the Hemingway Marina, west of Havana. "That there is a fine line between having grace and letting go of something you have no control over and you're just not going to beat Mother Nature maybe," she said. The treacherous body of water known as the Florida Straits is the holy grail for marathon swimmers. It has been conquered only once, by Australian Susie Maroney, who used a protective cage at age 22 during her 1997 swim that glided on ocean currents and enabled her to make the journey in just 25 hours. A native New Yorker, Nyad was raised in south Florida by a French mother and Greek-Egyptian stepfather. Her previous long-distance accomplishments include swimming around Manhattan island and a swim from the Bahamas to Florida in 1979. Nyad will have a small fleet of five support boats and a crew of 35 to keep her on course through the strong Gulf Stream current. Additional reporting by Rosa Tania Valdes; Editing by Tom Brown and Stacey Joyce