Marathon swimmer Diana Nyad's second bid to swim from Cuba to the Florida Keys is over.

According to her Twitter feed, Nyad was pulled from the water early Tuesday morning after swimming for 29 hours. She was about halfway in the journey that was expected to take 60 hours to cover at least 103 miles (166 kilometers).

Elaine Lafferty, who is on the boat according to Nyad's blog, posted on Twitter: "It's over." Lafferty says "the combination of factors was too much to safely continue."

The Twitter account reported she decided to end the swim herself, after "realizing the conditions of 5 to 10 knot winds and less than ideal currents."

An online chart plotting the swim's track showed the Gulf Stream currents pushing Nyad to the east of the intended course.

Nyad had hoped to end her swim at the Southernmost Point in Key West.

According to the Twitter feed, Nyad was on a support boat, wrapped in blankets.

Nyad tried to accomplish at 61 years old what she failed to do at 28 in 1978: swim an estimated 60 hours covering 103 miles from Havana to Key West, Fla. This time, she even attempting the swim without a shark cage, relying instead on an electrical field from equipment towed by kayakers to keep them at bay.

In her first attempt in 1978, she quit after being in the water for 41 hours and 49 minutes due to strong currents and rough weather that banged her around in a shark cage.