British-Australian marathon swimmer Penny Palfrey has set out on a record attempt to become the first person to swim from Cuba to the U.S. state of Florida without a shark cage.

The 49-year-old mother of three and grandmother of two dove into the sea off the Cuban capital, Havana, Friday morning.

Before beginning the 166-kilometer journey, she said she was filled with anticipation.

“It's a lot of work that's gone into this over the past year for my team, my husband, myself. A lot of training and a lot of support from [the commodore] and Hemingway International Marina, so it's all coming together, and so it's exciting to finally to get to this point where we can get started.''

Palfrey expects her swim through the shark-infested Florida Straits to take between 40 and 50 hours.

If she succeeds, Palfrey would break her own world record for the longest “unassisted ocean swim,” which she set last year when she swam 109 kilometers without a shark cage or wetsuit in the Cayman Islands, south of Cuba.

She told reporters Thursday that she was inspired to take on the Cuba to Florida swim when she flew from the Cayman Islands to Miami.

“As I say, when I was flying from Grand Cayman Island to Miami last year, I looked down, I could see this beautiful stretch of water and 'wow', I get on the atlas and I have a look at it and find out the currents and find out the water temperatures and find out the challenges ahead and by then I'm already hooked. Okay, I'm half way there, then I'll see if I can find a boat and a support team and everything else to go with it. And here we are!”

Palfrey's swim through the Florida Straits comes after 62-year-old U.S. swimmer Diana Nyad tried twice last year to make the trek without a cage, but was unsuccessful.

Australian Susie Maroney swam the straits at age 22 in 1997, but she used a shark cage for protection.

Instead of a cage, Palfrey is using equipment that emits an electrical field to keep the sharks away. She is being accompanied by a boat and support team.