Photo courtesy of IMDb
Director Mark Fischbach talks about ‘Iron Lung’ during a promotional interview.

With “Iron Lung,” Mark Fischbach — known to millions as Markiplier — makes the rare leap from YouTube titan to feature-film director, actor, editor and financier.

It’s an audacious move, and the resulting film reflects both the strengths and growing pains of a creator stretching into a new medium. Adapted from David Szymanski’s cult-favorite 2022 horror game, “Iron Lung” is a tightly contained sci-fi nightmare that thrives on atmosphere, tension and sheer creative willpower.

While not without rough edges, the film stands as a bold, earnest debut that proves Fischbach’s instincts as a storyteller extend far beyond the digital space that made him famous.

Set after a cosmic catastrophe known as the Quiet Rapture — an event that wipes out nearly all stars and habitable planets — the film follows a condemned prisoner forced into a desperate mission. His task: pilot a cramped, retrofitted submarine across an ocean of blood on a barren moon. The vessel’s forward viewport is welded shut, leaving him to navigate through flickering instruments and a camera that spits out grainy snapshots of whatever lurks outside. It’s a premise built on sensory deprivation, and Fischbach leans into that claustrophobia with confidence.

As the film’s lead, Fischbach delivers a performance that is raw, physical, and surprisingly restrained. Much of the movie rests on his shoulders — literally, given the single-location setting — and he manages to convey fear, frustration, and grim determination without slipping into melodrama. His background in expressive, personality-driven YouTube content could have easily worked against him, but instead he channels that intensity into something more grounded.

Caroline Rose Kaplan and supporting voices from Seán McLoughlin, Troy Baker, Elsie Lovelock, and Szymanski himself add texture to the world beyond the sub’s metal walls.

Visually, “Iron Lung” is a testament to practical effects and commitment. Reports of more than 50,000 gallons of fake blood aren’t just marketing flair — the film feels tactile, grimy and lived-in. The submarine set is convincingly oppressive, and the camera work emphasizes the suffocating lack of space. Fischbach’s editing choices occasionally veer into abruptness, but the pacing generally supports the escalating dread.

The film’s sound design, full of metallic groans, distorted comms chatter, and the unsettling churn of the blood ocean, does much of the heavy lifting in building tension.

Where “Iron Lung” shines brightest is in its understanding of isolation. The game’s core appeal — the terror of the unseen — translates well to film, and Fischbach resists the temptation to overexplain or overexpose. The horror is slow, creeping, and psychological.

When the film does reveal glimpses of what lurks outside the sub, the moments land with impact precisely because they’re used sparingly.

That said, the film’s ambition occasionally outpaces its resources. The narrative, by design, is minimalistic, and some viewers may find the story too sparse or the pacing too methodical.

The single-location structure, while thematically effective, risks monotony in stretches. A few sequences feel like they’re buying time rather than deepening the mystery or character. These aren’t fatal flaws, but they do highlight the challenge of expanding a short, atmospheric game into a feature-length film.

The production delays and long post-production period are evident in the film’s polish — some effects shine, while others feel slightly uneven. Yet even in its imperfections, “Iron Lung” carries a sincerity that’s hard to dismiss. Fischbach’s fingerprints are everywhere: in the editing rhythms, in the practical effects, in the willingness to take creative risks. It’s a film made by someone who cares deeply about the material and about proving himself as a filmmaker.

As a directorial debut, “Iron Lung” is impressive not because it’s flawless, but because it’s fearless. Fischbach could have played it safe with a comedy or a more conventional thriller. Instead, he chose a bleak, experimental, pressure-cooker horror story that demands patience and rewards attention. It’s a project that pushes him far outside the comfort zone of YouTube sketches and interactive videos — and he rises to the challenge more often than not.

In the end, “Iron Lung” is a grim, atmospheric and admirably committed piece of indie horror. It won’t be for everyone, but for fans of the game, fans of Markiplier, and fans of claustrophobic sci-fi, it’s a fascinating and often gripping experience. More importantly, it marks the arrival of a creator who is no longer just dabbling in filmmaking — he’s staking a claim in it.

If this is Fischbach’s first dive into feature cinema, it’s a promising one. And like the doomed submersible at the film’s center, he seems determined to keep pushing deeper.

Rating: R

Runtime: 130 minutes

Grade: B+

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Greg Williams is a reporter and Weekend Editor for The Sentinel. A Mifflin County native, he has been writing for The Sentinel since 1991.