By Miguel Marquez
KEY WEST, Fla. - Diana Nyad inspired the entire country with her historic Cuba-to-Florida swim. But now some marathon swimmers are taking a closer look at that feat. Was it too good to be true?
"We should never, ever give up," she said after her stunning achievement.
The record-breaking swim from Cuba to Key West, 110 miles and 53 hours in shark-infested water, is being questioned by some long-distance swimmers.
Among other things they want to know, did she really swim all 110 miles unassisted? Did she rest on a boat? Hold onto a canoe? Was she ever pulled along?
Skeptics speaking to National Geographic and blogging on The Marathon Swimmers Forum point to one nine hour stretch when Nyad sped up to more than twice her average speed.
They want her GPS, surface-current, weather, eating and drinking data released to verify her claim of conquering a swim once considered impossible.
CNN reached out to Byad's team, who promise a point-by-point response.
A historic swim and lifelong quest for Nyad, the fifth time was the charm. Now 64, she's tried to conquer this stretch of ocean since she was 29-years-old.
Barely able to move, she spoke to CNN's Dr. Sanjay Gupta just hours after her record-breaking feat.
"You know what's great about it Sanjay? It's all authentic. It's a great story," she said.
Its authenticity is not called directly into question, but in the uber-competitive world of long-distance swimming, an achievement of this magnitude is raising questions and demanding answers.