In this photo provided by Diana Nyad via the Florida Keys News Bureau, endurance swimmer Diana Nyad swims in the Florida Straits between Cuba and the Florida Keys Monday, Aug. 20, 2012. After being delayed by a weather squall line late Sunday night and early Monday morning, her team reported that Nyad was back on course in her effort to be the first swimmer to transit the Florida Straits from Cuba to the Keys without a shark cage. (AP Photo/Diana Nyad via the Florida Keys News Bureau, Christi Barli)

KEY WEST, Fla. - Diana Nyad slogged across the Straits of Florida for a third straight day Monday, advancing toward a swimming record on calm seas after enduring a night of stormy weather.

Nyad, who turns 63 on Wednesday, is making her third attempt since last summer to become the first person to swim from Cuba to Florida without a shark cage. She also made a failed try with a cage in 1978.

"She's doing well," a spokeswoman for the swimmer, Alex Crotin, said Monday afternoon.

Nyad had been expected to arrive somewhere in the Florida Keys early Tuesday, but her team tweeted Monday evening that she "lost six hours progress" in overnight storms Sunday. The team tweeted that a storm had blown Nyad off course and that "all hell broke loose" in the squall.

Monday offered far more ideal conditions, with blue skies and level seas and the Gulf Stream offering beneficial currents.

"The skies are clear, the sun high in the sky," crew member Brandon Beach wrote on Nyad's blog, calling it "a pretty gorgeous day out here in the middle of the ocean."

Nyad's team tweeted Monday morning that she was "swimming strong" in calm seas at 50 strokes per minute. She hit the 48-hour mark in the water on Monday afternoon; she estimated it would take at least 60 hours to reach Florida.

Australian Susie Maroney successfully swam the Straits in 1997, but she used a cage. In June, another Australian, Penny Palfrey, made it 79 miles (127 kilometres) toward Florida without a cage before strong currents forced her to abandon the attempt.

Nyad has already endured jellyfish stings on the current attempt. Stings forced her to cut short her second of two attempts last year as toxins built up in her system.

Nyad has been training for three years for the feat. She is accompanied by a support team in boats, and a kayak-borne apparatus shadowing Nyad helps keep sharks at bay by generating a faint electric field that is not noticeable to humans. A team of handlers is always on alert to dive in and distract any sharks that make it through.

She takes periodic short breaks to rest, hydrate and eat high-energy foods such as peanut butter.

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News from © The Associated Press, 2012