Last Breath will have you waiting to exhale.

Moving from documentary to drama should be a natural evolution, especially when you’ve already told the story once. But with Last Breath, director Alex Parkinson seems hesitant to explore the depths available in the genre, keeping one foot on narratively dry land rather than fully committing to an immersive storytelling experience. Instead we get an ersatz docudrama that remains tethered to journalistic restraint.

Diver Chris Lemons may be the film’s focal point, but he’s also, necessarily, its most passive figure – unconscious for much of the runtime as his colleagues fight to save him. Finn Cole brings what little he can to the role, but the real heavy lifting is left to Woody Harrelson’s genial Duncan Allcock and Simu Liu’s resolute Dave Yuasa. Together, they shoulder the emotional weight, their performances crackling with urgency and genuine camaraderie, turning the film’s submerged sequences into something truly visceral and utterly gripping.

It’s on the surface the film’s momentum drains away. Parkinson’s dedication to procedural realism leaves the bridge crew feeling oddly detached, their emotionally inert reactions to events – including the failure of their ship’s entire computer system – undercutting the tension rather than heightening the drama. It’s one thing to strive for authenticity, quite another to strip moments of crisis of their potency. With Harrelson and Liu, there’s an almost unbearable sense of exigency but on the bridge, you’d think they were waiting for the kettle to boil for their afternoon cuppa. Eventually they do begin to move and act as if there’s some sense of urgency but even then it all feels a little staged and “dramatic recreation”-y to sit alongside the nerve-shredding tension of the underwater scenes.

It also doesn’t help that the core story, dependent as it is on a ticking clock and very specific timing, isn’t quite long enough to sustain a feature-length and with little interest in or provided by the bridge crew, Last Breath bookends its drama with rote domestic scenes before and after the crisis. While these moments offer some insight into Lemons’ personal life, they feel perfunctory – and don’t add much depth beyond what’s already conveyed through the central performances, leaving them feeling more like obligatory runtime fillers than essential storytelling.

When Parkinson lets the story sink into its inherent terror – the oppressive vast darkness of the deep sea, the helplessness of the men above, the narrowing odds of survival – Last Breath really works. But for every moment of nerve-fraying intensity, there’s another that feels frustratingly restrained. There’s a compelling film in here somewhere, and when it clicks, it’s excellent. But Parkinson never quite lets go of his documentarian instincts, leaving Last Breath feeling like it’s stuck in decompression, not quite ready to embrace the dramatic depths it could have explored.