HAVANA (CBSMiami/AP) — A British-Australian grandmother has entered the waters off of Havana to attempt a record swim from Cuba to Florida.

Penny Palfrey, 49, aims to be the first woman to swim the Straits of Florida without the aid of a shark cage. Instead she’s relying on equipment that surrounds her with an electrical field to deter the predators.

Palfrey, a mother of three and grandmother of two, estimates that the swim, if successful, will take 40 to 50 hours.

Australian Susie Maroney made the crossing in 1997 at age 22 with a shark cage.

American Diana Nyad made two cageless attempts last year but fell short of her goal. She plans to try again this summer.

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