In many ways, Nyad adheres devotedly the the patterns of most modern biopics. The film strives to convey something close to the totality of its central subject, long-distance swimmer Diana Nyad (Annette Bening) through focusing the plot on one central quest. In this case, the story follows Diana’s attempt while in her sixties to swim from Cuba to Florida, a feat she’d failed at some three decades earlier, one of the few unmet challenges in her career. Diana recruits her longtime friend Bonnie Stoll (Jodie Foster) to be her coach, and together they assemble a crew of supporters, included the skilled sea navigator John Bartlett (Rhys Ifans). The rhythms of the Nyad are familiar from kindred films, notably those set somewhere in the wide world of sports. What sets Nyad apart are the handful of characteristic that stray from well-worn expectations.

First and foremost, Diana is often a hard person to root for in the film. However Diana Nyad is in real life, within the frames of Nyad she’s exceedingly difficult. She’s self-centered, combative, and slow to express gratitude to the gaggle of people who regularly set aside their own ambitions to pursue her unlikely dream. Bening is ferocious and phenomenal in the role. Long an actress whose comfortable setting aside vanity, Bening commits to the wrenched physicality and scorched emotions of the character with equal vigor. Accentuating that intensity is the loose-limbed nimbleness of Foster’s performance, easily her best in many, many years. Through Foster, Bonnie becomes a kind of surrogate for the audience, making it plain how rough it is spending time in Diana’s wake.

Nyad also carries some interesting reverberations of the filmmaking background of its directors, Elizabeth Chai Vasarhelyi and Jimmy Chin. The duo previously specialized in documentaries, including the Academy Award–winning Free Solo. Nyad is their feature directorial debut, and they carry over a willingness to incorporate actual footage that fictionalizations often avoid. The opening of the film uses so much material of the real Diana Nyad that viewers would be forgiven for thinking they accidentally clicked an actual documentary about the swimmer, and there are moments throughout where they casually incorporate news footage without particularly disguising that it has Diana rather than Annette. What could be distracting instead tethers the film powerfully to the reality it is drawn from.

There are pieces of Nyad that don’t particularly work. I found some of the fragmented flashbacks to be needlessly fussy, as if the directors were attempting to bring in visual flair to break up what they perceived to be the relatively monotony of scene after scene of Diana’s long swim. The troubled history those glimpses of the past convey is usually better handled in the well-crafted dialogue in Julia Cox’s screenplay, especially as acted by Bening and Foster. And it’s hard to deny that the storytelling beats are sometimes too familiar; the film almost becomes a victim of its own sturdy construction. Where Nyad excels, though, it moves with as much power and assurance as the woman it depicts.