Diana Nyad made history last week, becoming the first person to ever complete a swim from Cuba to Florida without the benefit of a shark cage.
There are some, however, that are calling into question the integrity of the 110-mile, 53-hour swim.
According to the Associated Press, a group of fellow marathon swimmers are questioning a certain stretch of Nyad's swim, when she apparently doubled her speed in the water. Skeptics believe she was perhaps aided by boats along the way.
Andrew Malinak, a long-distance swimmer from Seattle, used data from Nyad's website to investigate the swim.
"When you know how hard it is, you kind of want those details," Malinak told the AP.
The stretch in question came after Nyad was in the water for about 27 hours. According to the data from her GPS tracking device, Nyad increased her speed from about 1.5 miles per hour to more than three miles per hour for a seven hour stretch.
To skeptics, this jump in speed indicates a questionable change. But Nyad's team has stood firm, attributing the increased speed to favorable weather conditions.
"At some points we were doing almost 4 miles an hour," team navigator John Bartlett told the AP. "That's just the way it works. If the current is in your favor at all, that explains it."
An oceanographer independent of Nyad's crew agreed, saying that the swim could not have taken place at a more convenient time.
Still, Bartlett says all data collected regarding the swim will be submitted to three open water swim organizations and the Guinness World Records for final verification.