The 64-year-old swam 110 miles for 53 hours in shark infested waters but other athletes now want to know did she really swim completely 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 9 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.
Nyad's team promise a point-by-point response.