Diana Nyad's real life trainer says Jodie Foster nailed the role: 'I thought it was me'

Bonnie Stoll is not a woman who's easy to fool - but Jodie Foster pulled it off.

The Oscar winning actress plays the former racquetball champion in Nyad, the story of endurance-swimmer Diana Nyad who aged 60 decided to re-attempt the punishing 110-mile swim from Cuba to Florida which eluded her in her youth.

Stoll, who was both Nyad's best friend and professional trainer, tells Sky News: "The first time I saw [the film], I definitely thought it was me…

"It's surreal and unbelievable and a real tribute to this actor. I mean, she did it. It surprises me almost every time I see the movie and I see it quite a bit. I think it's me up there."

Foster, 60, is reported to have completely immersed herself in Stoll's way of life: training, nutrition, supplements, workouts, everything.

Quickly noting Stoll's "salt of the earth quality," she described her as "the kind of person you'd want to be in a storm with". Which is lucky, because the movie has several storms to get through.

Annette Bening too - who plays Nyad in the film - trained for over a year to get into peak physical condition for the role, which of course demanded prolonged stretches of swimming.

World class actors, meeting a world class athletes and making a movie together. It's a recipe that Netflix will be hoping might be a hit with the critics.

The movie re-creates some of the most challenging moments of the real-life crossing, which was completed without the use of a shark-cage, despite the risk of predator infested waters.

But it was not sharks that turned out to be the biggest problem.

Stoll explained the biggest threat to their success came from deadly box jellyfish.

"We did not expect them. We had no idea they were already in the Gulf. But it was not a pleasant surprise... It was kind of a nightmare."

She explains how Dr Angel Yanagihara, a bio-medical researcher considered to be one of the world's pre-eminent experts in box jellyfish, helped them overcome the potentially fatal sticking point by helping design a mask.

However, that came at a cost.

"Diana was getting prosthetic for her face, the mask, so the box couldn't get in. And then we heard about a box getting into someone's mouth and they swallowed it. And that was not a good result.

"The swimming in that mask was a nightmare, for me especially. I can't even look at it. It's claustrophobic."

The film's director, Chai Vasarhelyi says they replicated everything Diana wore down to the last detail: "It was that authentic. The same suit that Diana wore, the same goggles, everything".

And while they had two silicone face masks made for Bening to wear, Vasarhelyi admitted: "It was so painful we cut out the mouthpiece".

It's a move Stoll approved of, echoing: "Good, good".

Vasarhelyi worked with her husband, professional climber, skier, filmmaker and photographer Jimmy Chin on the film, and the couple have two young children together.

She explained: "It was a really good way of keeping the family together all in one spot and who knew that you can grow in your forties? That you can grow after 12 years of marriage?"

The couple's past films together include The Rescue (the rescue of 12 boys and their coach from a flooded cave in Northern Thailand) and Free Solo (an Oscar-winning portrait of rock climber Alex Honnold).

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Vasarhelyi summed up their unique area of interest as, "stories about humans who push the possibility".

And proving that working with your partner isn't necessarily the recipe for disaster that many might assume, she joked: "We were such old news, you know, me and him. But suddenly, like, we just got stronger. We got better. We saw what each other does even more clearly. And the kids had a great time."

She added: "It ultimately caused some real deep changes afterwards about how we went, the way we work together."

It seems the Nyad magic - that propelled the film's real-life protagonist to wake up one day aged 60 and decide she wasn't done - has rubbed off on its director.

And that is just the sparkle Netflix will be hoping makes its way into voters' hearts come awards season.

Nyad is streaming now on Netflix.