Making a movie about 64-year-old Diana Nyad’s 110-mile swim: ‘She wasn’t bothered about sharks. The box jellyfish we didn’t know about’

In 1978, Diana Nyad, then 29, decided to swim from Havana to Key West, Florida. Like everything else this endurance athlete does, she made the challenge seem like no biggie: a natural progression, even, for someone whose surname is derived from the word “naiad” (water nymph) and who has been accused of having a “superiority complex”. At about 110 miles, the journey would dwarf her previous accomplishments, such as circling the island of Manhattan in just under eight hours. But it wasn’t to be. Violent storms put paid to her attempt after she had covered nearly 80 miles in 42 hours and been blown far off course.

Nevertheless, the Havana-to-Florida dream endured. As her 60th birthday loomed, and with three decades behind her as a sports broadcaster, Nyad set out to have another crack at it. Unlike the previous time, she would not be swimming inside a shark cage; instead, there would be shark divers and electronic “shark shields” to deter any Jaws wannabes in the vicinity. And there was another weapon, every bit as vital to her success: Nyad’s devoted, tough-cookie BFF Bonnie Stoll, whom she enlisted as her coach. Stoll watched over her from the accompanying boat throughout the various abortive attempts during which Nyad was thwarted by bad weather, deadly box jellyfish and a severe asthma attack. Her eventual triumph came in 2013 at the age of 64.

The story of that 53-hour swim has now been turned into a stirring Netflix film, Nyad, directed by Jimmy Chin and Elizabeth Chai Vasarhelyi, the husband-and-wife team who are making their narrative feature debut after winning an Oscar for their breathtaking climbing documentary Free Solo. Annette Bening is ferocious as Nyad, her face as raw and salty as an old sea dog’s; Jodie Foster is in marginally softer mode as Stoll.

As a member of the Sag-Aftra actors’ union, the swimmer is not publicising the film during the current strike, but the 72-year-old Stoll has agreed to step in. Nyad is no slouch when it comes to self-promotion whereas her former coach prefers to hover in the background. Not that anyone is likely to confuse Stoll with a shrinking violet. This former racquetball champion, who still trains Hollywood actors for physically demanding roles, strides into the hotel suite where I am waiting, plonks herself in an armchair and wastes no time voicing her concerns about the film. “I was worried it would be a chick flick,” she says, fixing me with a stare that penetrates the smoky lenses of her glasses. “It’s not a chick flick. It’s a great movie, right?” Having received the answer she wanted, she gives a nod. “Good,” she says.

Chick flick or not, it is highly refreshing to see a Hollywood movie in which the main characters are two uncompromising lesbians in late middle-age. The pair met about 40 years ago and dated briefly. “But we were better at just being two golden retrievers running around together,” Stoll tells me. As she talks, I notice a tattoo on her wrist. “Diana and I have the same one,” she says. “Mine is subtle. Hers is huge, covering part of her leg.” She rolls her eyes, as if to say: typical her. “It says, ‘ishin denshin’, which means ‘One heart, one mind’. But not a lot of chatter. Which is what it was like on the boat.”

Ah, yes, the boat. What on earth made her think that Nyad, at 60, would be able to complete the daunting and treacherous swim? “I went with her to Mexico where she was doing her training, and it was clear: she belongs in the water. She’s so comfortable there. She wasn’t bothered about sharks. The box jellyfish we didn’t know about. They were never in the Gulf before. The moon jellies, the man o’ war – they’ll hurt you but they won’t kill you. The box can kill.” They almost did. Nyad was stung badly, as was the doctor who leapt into the water to help her. On the next attempt, she donned a bespoke silicone mask to protect her from a repeat attack. Wearing it on screen makes Bening look fantastically monstrous and spectral, like some outlandish ghoul from Spirited Away.

Stoll says it is the mental focus that really sets her friend apart. “There are very few people in the world who test the will of the human being. I’ve never seen tunnel vision like that.” Except for one other person, she says: Chin, the film’s co-director. “He’s this crazy mountain climber. He’s got it, same as Diana. He was at Everest recently.”

In fact, says Vasarhelyi when we meet later, Chin is on his way home. “He didn’t make it,” she says. “They had weather complications.” Her expression, though composed, has a longsuffering quality to it. “I knew exactly who I was marrying and I love him very much,” she says diplomatically.

She finds herself in the same position as Stoll: looking on supportively as her best friend’s life is imperilled in the pursuit of a dream. “Bonnie’s journey in Nyad is interesting,” she says. “It’s not dissimilar to me and Jimmy. It’s like: ‘I know what you do is dangerous but I can’t take that from you. So we might as well be here together.’”

One of the couple’s former subjects is Elon Musk, who featured in their 2022 documentary Return to Space, about the Space X/Nasa mission. What do Nyad and Musk have in common? “Vision and drive. Look, Diana even offered to do all the stunt swimming. We said: ‘No thank you.’ At one point, she said: ‘I can play myself!’ But that’s Diana for you.” In the late 1970s, Nyad claimed to have written a Rocky-style script about her own career. In 2019, she starred as herself in the off-Broadway play The Swimmer, which she also wrote; she even roped in a reluctant Stoll, who sat at the top of a lifeguard station on stage, script in hand. “Diana turns everything into a production,” sighs Stoll, rolling her eyes for the umpteenth time.

It is striking how frequently she plays down her own contribution to her friend’s success. “Diana’s the best friend you could have in the world,” she says. “Much better than I am.” Why do you say that? “She has unconditional love. I only have that for a pet.” Not for Diana? “Sometimes I really don’t like her. She’s so stubborn. There are times when I want to knock her down.” She shakes her head. “I probably shouldn’t say that.” But you see each other every day. And you still love her, right? “Love? Yeah.” That sounds unconditional to me. “OK, then, you call it that,” she says, in a tone that suggests she has had enough of my crap.

Her patience seems fully exhausted when I mention that the swim has never been ratified by the World Open Water Swimming Association, which has advised viewers to watch the movie “with discernment, keeping in mind the discrepancies about the swim”. Questions linger over the ways in which some of the data was recorded (or not) during the swim, and there is a whole website devoted to challenging claims Nyad has made about her achievements. Her supporters, though, think these attempts to discredit her are motivated by homophobia and sexism. “I feel very liberated by the idea that a woman can be complicated and have sharp elbows,” offers Vasarhelyi.

When I ask Stoll whether she thinks ratification will ever happen, she interrupts me: “It doesn’t matter! She did it! There are 41 people on our team that say she did it.” Does the film represent a kind of ratification? “I hope so.” What did she learn from watching it? “I learned I do this a lot.” She wipes her upper lip with her finger, as though erasing a milk moustache. “I never knew. Jodie was unbelievable. I thought it was really me up there.”

I tell her my favourite scene is when Foster, as her, jumps in the water to give Bening/Nyad a morale boost during the last stretch of the swim, encouraging her to do one more stroke, then another, just as her momentum is flagging. Stoll, it turns out, also had tears in her eyes watching that. “I thought it was brilliant,” she says brightly. “I’m just sorry I didn’t do it.” Huh? “Listen, I never jumped in. I never thought of it. I wish I had now.” Ah well, that’s movies for you: even better than the real thing.

• Nyad is in cinemas from 20 October and on Netflix from 3 November