As a pitch for a movie, the story sounds preposterous.

A 28-year-old swimming phenomenon fails to realize her dream accomplishment − doing the crawl from Cuba to Florida − only to decide that she wants to try one more time, at age 64.

And yet that's the real-life tale behind "Nyad" (streaming now on Netflix), the story of athlete Diana Nyad and her indefatigable coach Bonnie Stoll, played with gusto and guts by Annette Bening and Jodie Foster respectively.

So how much of "Nyad" is true? USA TODAY spoke with Stoll as well as husband-and-wife co-directors Jimmy Chin and Elizabeth Chai Vasarhelyi (2018 Oscar winners for the climbing documentary "Free Solo") to break down the details of the 2013 epic endeavor.

Did Diana Nyad actually swim all the way from Cuba to Florida unassisted?

Stoll, who "watched every stroke of that swim," says the record is unquestionable. That said, some have done just that ever since Nyad reached the shores of Key West.

Shortly after the swim ended, critics questioned how Nyad could have made the swim in those 53 hours, given that GPS coordinates suggested unusual speeds for certain segments of the swim. Others complained there weren't enough independent monitors for the feat, or that she might have been aided by crew.

Nyad has repeatedly rejected such claims, citing everything from speed-boosting currents to jealousy. Chin, an accomplished professional climber, says there are very few athletes who push the limits of their sport without generating detractors. "Everyone has naysayers," he says.

Did Bonnie Stoll walk out on Diana Nyad after her failed attempts to swim to Florida?

That conflict was created to keep the plot of "Nyad" taut, Stoll says. In reality, while there was a break during failed attempts to swim to Florida, Stoll was never going to throw in the towel as coach.

"That split in our relationship never happened," she says. "For about five months, I wasn't working with Diana, that's true. But we'd see each other every day. She wasn't allowed to say, 'Bonnie please come help me again,' and I wasn't allowed to say, 'Diana don't do this.' "

The two still talk every day, although Nyad of late has been writing children's books and "spending three hours or more a day on the tennis court," says Stoll.

Is Diana Nyad as prickly and unpleasant as 'Nyad' depicts?

No one who knows Nyad disputes the fierce nature of her personality, almost a requirement for trying to accomplish the unthinkable. "I love that we did a movie about a woman who is a 360-degree personality who is not afraid to be hungry and ambitious," says Vasarhelyi. "Our film isn't about a record, it's about a woman who woke up at 60 and felt the world was done with her, but she wasn't done with the world."

While Nyad certainly can be gruff and bullheaded, her longtime friend Stoll says that is just one facet of her personality that had to be dominant to power the movie.

"They did nail that part of her personality, the tough part," she says. "But what you see less of is what a bright person she is, someone who speaks six languages. And she would never speak to her team disrespectfully, as the movie sometimes showed. She just had tunnel vision, which made the 40 of us going for the ride with her equally focused."

Did Annette Bening do her own swimming in 'Nyad'?

Bening, 65, who embarked on the film at roughly the same age as Nyad during her successful crossing, was fully committed to the role from Day 1, say the film's co-directors. "Annette was our secret sauce," says Vasarhelyi. "She and Warren (Beatty) have a nice pool at home, and she got to it.

For a year, Bening worked on endurance and replicating Nyad's swimming form with an Olympic-caliber coach. When she showed up on the film's set in the Dominican Republic for the 37 days of in-tank water scenes, she astounded the crew.

"Annette jumped in the water tank and instantly you could see the form and strength were there," says Vasarhelyi. "She ended up being able to spend between four to eight hours a day in the water, which was invaluable for the shoot. We had three stunt swimmers who basically just did water safety stuff." Stoll adds: "I hear Annette now has a new hobby, and still swims daily."

Did Annette Bening and Jodie Foster really go makeup-free in 'Nyad'?

Both Bening and Foster were adamant. "They said, 'Our bodies cannot be touched up,' " says Vasarhelyi. "That was the point, the experience had to be real, and look real. Those abs on Jodie are real."

For most of "Nyad," Bening's hair and body are sunbleached or worse, especially after scenes in which deadly box jellyfish sting her, scuttling yet another crossing attempt. The directors say neither actress wore any makeup, in keeping with the no-nonsense personalities of the women they were portraying.

"This film feels like a miracle," says Vasarhelyi. "If you said you'd have these two documentary filmmakers trying to make a feature film about two older lesbians and it all takes place in water, I would not give you great odds. But it worked out because everyone was committing to doing a film that we rarely see, about older women in their full splendor and complexity."

What's next from the directors of Netflix's 'Nyad'?

Chin and Vasarhelyi landed in the spotlight after their Oscar win for "Free Solo," the story of solo climber Alex Honnold's impossible climb without ropes up a sheer face in Yosemite National Park in California. Since then, their documentary projects have included a look at the cave rescue of the Thai soccer team (2021's "The Rescue") and the story of conservationist Kris Tompkins (2023's "Wild Life").

And while they thoroughly enjoyed jumping into the feature film world, their next endeavor is in familiar territory.

"Our next project takes us to Antartica, for a documentary with National Geographic on the amazing discovery of (British explorer Ernest) Shackleton's boat, The Endeavor," says Vasarhelyi. The story revolves around Shackleton's 1914 expedition, which ended a year later when the boat became trapped in ice and sank. The explorer managed to somehow get his crew to safety. Also on board for the project is British director Natalie Hewit.

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