MIAMI -

When Diana Nyad came ashore on Key West last week, she became the poster child for perseverance. She completed her marathon open water swim from Cuba, 110 miles in 53 hours. It was a record swim by the 64-year-old on her fifth attempt.

Now some in the swimming community are doubting Nyad, saying it's too good to be true. Some have been debating on social media and in online forums whether the 64-year-old endurance athlete got into, or held onto the boat accompanying her.

Online bloggers say there are inconsistencies in her data, including hours unaccounted for, and they are skeptical of the fast pace she swam toward the end of her journey.

"One-hundred percent guaranteed she swam from shore to shore" said Steven Munatones.

Munatones was on three of Nyad's previous attempts.

"I have seen her wracked with pain and refuse to get out of the water, " said Munatones.

"I think it's more jealousy than fair criticism," said Jonathan Strauss. "Anyone would want to do what she did."

Strauss plans open water marathon swim events in South Florida. He says it's a relatively new sport with few rules. Nyad's swim showed their sport and it's unique challenges.

Some of Nyad's critics also question whether she violated the traditions of her sport -- many follow strict guidelines known as the English Channel rules -- by using a specialized mask and bodysuit to protect herself from jellyfish.

"There is potential for jelly fish, sharks," said Strauss.

Nyad's team helped keep away from sea creatures, and local 10 meteorologist Trent Aric said the weather conditions were prime for Team Nyad.

"Weather wise, she had a perfect forecast the entire way, and she may have gotten a little help from the Gulf Stream," said Aric. "When she has a current in her favor, it can add three or four miles per hour."

From the the weather data from that day, it appears that she did. Still, detractors want more proof that Nyad stayed in the water the whole way. They say she could not have picked up as much speed as she says she did from the fast-moving Gulf Stream current.

Some swimmers analyzing the available data say Nyad, who has said she tends to swim at a speed of roughly 1.5 mph, appeared to maintain sprinter's pace or faster for a considerable amount of time.

Her navigator, as well as one of the swim's two official observers, told The Associated Press over the weekend that Nyad swam in favorable currents the entire distance herself without aid.

According to Alexandra Crotin, one of Myad's spokeswomen, Nyad is currently in California but has heard the criticism and plans to respond to it on Tuesday.