“Iron Lung” is honestly one of the most uncomfortable movies I’ve watched in a while, and I mean that in a good way. The film, directed by and starring Markiplier, is based on the indie horror game of the same name. The story takes place in a future where most of the stars and habitable planets have mysteriously vanished. As a last resort, scientists discover a moon covered in a massive ocean of blood. A prisoner is forced to pilot a tiny submarine into that ocean to explore it, with the promise of freedom if he survives.

Most of the movie takes place inside the cramped submarine, making it feel extremely claustrophobic. There are barely any windows, and most of the time, the audience sees only blurry photographs from the submarine’s external camera. This actually makes the horror stronger because your imagination fills in what you can’t see. The red lighting inside the submarine gives everything a tense, almost suffocating feeling. The sound design also stands out—every metallic creak and distant noise feels important, and it keeps you on edge the whole time.

As the movie progresses, the prisoner starts to mentally unravel. Being alone in total darkness, surrounded by a literal ocean of blood, clearly takes a toll on him. The ending is especially disturbing when the submarine is violently attacked by something massive beneath the surface. The film doesn’t fully explain what the creature is, which makes it even scarier.

Overall, “Iron Lung” isn’t a typical jump-scare horror movie. It’s slow, psychological, and very tense. Some people might think it’s too minimal or repetitive, but I think that simplicity is what makes it effective. It feels experimental and risky, but it commits fully to its concept. For a movie based on a small indie game, it’s intense.