Iron Lung review: Mark Fischbach's claustrophobic sci-fi horror thrives on dread

Set after a cosmic catastrophe, Iron Lung follows a lone prisoner sent to explore a blood ocean. Headlined by Mark Fischbach, the film is based on the indie horror game by David Szymanski.

The scariest thing about Iron Lung isn’t what you see, it's what you can’t. For most of its runtime, Mark Fischbach’s claustrophobic sci-fi horror keeps you trapped inside a rusting submarine with barely any room to breathe.

The film shuts the hatch early on and almost never opens it again. What lies outside? A vast ocean of blood on a distant moon. What lies inside? One man, a failing vessel, and the creeping realisation that something might be moving in that ocean.

Based on the indie horror game by David Szymanski, Iron Lung marks the filmmaking debut of the YouTuber, also known as Marklipier, who writes, directs and stars in the film. And to his credit, he doesn’t try to turn it into a loud, jump-scare-filled horror spectacle. Instead, he leans fully into dread: the slow, creeping and unsettling kind.

The premise is absolutely grim; the universe is basically dead. After a mysterious cosmic disaster known as the Quiet Rapture, every star and habitable planet has vanished. Humanity survives in scattered pockets across space, clinging to whatever resources remain. Fischbach plays Simon, a convicted criminal sent on what is essentially a suicide mission. His job: pilot a crude submarine called the Iron Lung through an ocean of blood discovered on a remote moon and photograph whatever lies beneath the surface. The catch? The submarine has no windows.

Simon navigates using coordinates and instruments while periodically firing an external camera to capture grainy photographs of the ocean floor. These images flash briefly on a screen and you are constantly trying to make sense of what you’re seeing before the film pulls you back into the submarine’s suffocating interior.

And that’s where Iron Lung is at its best. The film thrives on atmosphere. Pipes rattle, the hull groans and gauges flicker nervously. Every sound feels slightly wrong, and you feel the vessel itself knows it shouldn’t be here. The ocean outside also becomes more terrifying with every passing moment because the film refuses to show it clearly.