NEW YORK, Sept 10 (Reuters) - U.S. long-distance swimmer Diana Nyad on Tuesday vigorously defended her record-breaking, 110-mile (177-km) swim from Cuba to southern Florida after skeptics raised questions about the grueling trek.
"I swam ... in squeaky-clean, ethical fashion," Nyad said in a conference call late Tuesday that included journalists and fellow marathon swimmers, some of whom have publicly questioned aspects of her exhausting journey.
"I honored the rules," Nyad said at the start of the conference call. "I was an ethical swimmer."
A triumphant Nyad, 64, staggered ashore in Key West, Florida on Sept. 2, after having swum about 53 hours, to become the first person to complete the treacherous crossing without a shark cage.
Nyad's swim was her fifth and only successful attempt.
The highly publicized crossing has sparked a social media debate about whether her journey meets the requirements to break the world record.
Some have questioned how Nyad was able to more than double her pace about halfway to Florida, and have wondered whether she was towed at any points by tracking boats.
Marathon swimmer Evan Morrison was among a number of members of the long-distance swimming community who publicly questioned Nyad's feat on social media.
"In reading through Diana's crew's live-blog, trying to suss out how this incredible swim happened, I was struck by how little information there actually was," Morrison wrote on the online Marathon Swimmers Forum.
"These details matter because Ms. Nyad is claiming - and the media reporting without fact-checking - a new world record for longest-distance nonstop, unassisted ocean swim," he said.
Nyad's pace quickened significantly about halfway through the swim - from her average 1.5 miles per hour (2.4 kph) to nearly four miles per hour (6.4 kph) - a swift pace that continued for about six hours.
She and her supporters have said that she got a significant boost from a favorable Gulf stream current - a contention that independent experts who study the ocean currents in the region agreed with Tuesday.
Mitchell Roffer, who runs a Melbourne, Florida-based ocean fishing forecasting service, said Nyad caught a swift, north-moving current, and then turned east out of the current at precisely the right moment.
"To me, it was an oceanographic lotto that she hit," Roffer told Reuters. "You can't get much luckier than she did."
"The current, which was pulling her in north-northwestern flow, was as perfect as you could get," Roffer said. "It would explain why her speed was faster during that period."
John Bartlett, one of Nyad's navigators, said on the call Tuesday that Nyad's speed for nearly six hours - beginning about halfway through the trek - averaged 3.97 miles per hour (6.39 kph)
The previous record was held by Australian Penny Palfrey, who attempted the same crossing without a shark cage in 2012. Palfrey swam about 80 miles (129 km) in 41 hours before adverse currents forced an end to the attempt. (Reporting By Chris Francescani; Editing by Tim Gaynor and Eric Walsh)