Diana Nyad is defending her 110-mile swim from Cuba to Florida against sceptics who ask whether she got into or held onto a boat during part of the journey.

Nyad said she swam without holding onto any of the boats or people accompanying her.

"I swam. We made it, our team, from the rocks of Cuba to the beach of Florida, in squeaky-clean, ethical fashion,'' Nyad said.

Critics

Her critics are suspicious about long stretches of the 53-hour swim where Nyad appeared to have either picked up incredible speed or to have gone without food or drink. Since Nyad finished her swim September 2, long-distance swimmers have been debating it on social media and in online forums.

Nyad's speed, at some points more than doubling, has drawn particular scrutiny. Her team has attributed her speed to the fast-moving Gulf Stream flowing in her favour.

The 64-year-old endurance athlete and her team held a conference call with some of the sceptics who questioned her navigator's credentials and observations of the currents.

Nyad's navigator, John Bartlett, said her fastest speed averaged about 3.97 mph over a 5.5-hour period over about 19 miles, crossing the strongest parts of the Gulf Stream, which was flowing at a favourable angle.

"What you're seeing is the combination of the speed of Diana propelling herself in the water and the speed of the current carrying us across the bottom,'' he said.

An oceanography professor at the University of Miami said data collected from a research buoy drifting in an eddy referenced by Bartlett confirms that ocean currents contributed as much to Nyad's speed as Bartlett said they did.

The eddy appears periodically in that region, and it alters the course of the Gulf Stream.

"So, if you're close to (the eddy), you're going to benefit from it, too,'' Tamay Ozgokmen said.

"I don't have trouble believing that she said she essentially doubled her speed during her swim, because of the ocean currents.''

Evan Morrison, co-founder of the online Marathon Swimmers Forum, says it will be interesting to compare observations made by Nyad's navigator with publically available data about the currents Nyad swam.

Nyad attempted the swim from Cuba to Florida four times before finally completing the journey on her fifth attempt, making her the first to make it without the aid of a shark cage.

She used a specialised mask and bodysuit to protect herself from venomous jellyfish, which are considered a more serious threat than sharks in those waters. Some members of the marathon swimming communities say the methods violated the traditions of her sport.

Source: AP