What started as a small, cult-favorite horror game built on pure atmosphere has turned into something way bigger than anyone expected. Iron Lung is not a product of classic Hollywood studios or big-name directors. Instead, it comes from a YouTuber who built his career playing horror games online and decided to turn one of them into a full movie himself.

Taking on directing, writing, editing, and even starring in the film, Markiplier, whose real name is Mark Fischbach, went all in on what is essentially a massive passion project. And somehow, it paid off. With a relatively small budget of around $3 million, Iron Lung still managed to pull in over $34 million worldwide and expand into thousands of theaters, proving that something this strange and experimental could actually find a real audience.

The movie takes place after a massive cosmic event known as the Quiet Rapture, during which entire planetary systems suddenly disappeared. Humanity is barely hanging on, scattered across what little remains. Then a strange discovery is made: a moon completely covered in an ocean of blood.

To explore it, they send down convicts in a small, rusted submarine. The main character, Simon, played by Mark Fischbach, is one of them. He is sealed inside this cramped sub and sent into the unknown with almost no visibility, relying only on instruments and a camera system to navigate. From that point on, the movie shifts its focus from the mission to survival and the fear of what might be out there.

Iron Lung stands out for its tense atmosphere. With only one primary setting and actor for most of the film, it never feels empty. Sound design does much of the work; every metallic creak and distant noise is intense, especially in the claustrophobic environment. You feel trapped alongside Simon. The lighting, often limited to dim screens and brief flashes from the camera, adds to the unease. You never fully see outside the submarine, making everything more unsettling as your imagination fills in the blanks.

Since the movie depends so heavily on one person, Mark Fischbach really had to carry it. Overall, he does a solid job. His performance feels raw and stressed in a way that fits the situation. You can tell his character is slowly breaking under the pressure. There are a few moments where the acting does not fully hit the emotional level it is aiming for, but considering how much he took on behind the scenes, it is still impressive. The character ends up feeling believable, which is important for a film like this.

The story itself is where things might get mixed reactions. At first, it was pretty straightforward, focusing on the mission to explore the blood ocean and survive any dangers within. But as the movie goes on, it introduces unclear events and visual sequences that aren’t fully explained. The narrative starts making less sense on the surface and invites viewers to interpret what could be happening, rather than spelling out every detail.

Some people will probably like that shift because it adds a feeling of unpredictability and makes the film more unique. Others might find the unexplained scenes and lack of clear answers confusing, or make it harder to stay connected to the story. Not every experimental idea fully works, but it is definitely more interesting than playing it safe.

In the end, Iron Lung is not a movie for everyone. It is slow, tense, and heavily focused on atmosphere instead of action, which can be a turnoff if you are expecting something fast-paced. But if you are into that kind of horror, it really works.

If you are a fan of Mark Fischbach, enjoy psychological or sci-fi horror, or like films that lean more into mood and mystery, this is definitely worth watching. It also helps if you are familiar with the original game by David Szymanski, or are willing to check it out after, since it adds another layer to the experience. If you like movies similar to Event Horizon or Annihilation, there is a good chance this will be your kind of thing.

My final rating: ★★★★★

Based on the game by: David Szymanski

Screenplay: Mark Fischbach and David Szymanski

Music: Andrew Hulshult

Runtime: 2h 5m (125 minutes)

MPAA Rating: R

Genre: Sci-Fi Horror / Psychological Horror