By Luke Thomas, February 10, 2026
Very early on in “Iron Lung,” a down-on-his-luck Simon, welded into a scrappy SM-15 submersible engulfed in an ocean of blood, asks an intercom what exactly he’s supposed to be searching for amid a red sea, to which the voice over the intercom plainly admits “I don’t know.”
This is the sentiment I would soon share through the rest of my viewing of the film.
That’s not meant to be a dig on YouTuber Markiplier’s directorial debut, not entirely at least, as “Iron Lung,” based on David Szymanski’s 2022 game of the same name, opts to guide the audience through the film with seemingly as little information as necessary.
Of that information, what’s known is “Iron Lung” takes place after an event named “The Quiet Rapture” has left the universe practically empty. All stars and habitable planets have vanished, while only a sparse number of moons and space stations remain.
Imprisoned for being implicit in the destruction of one of those stations, Markiplier’s character Simon is given a chance at freedom if, although he doesn’t get much of a choice, he explores the aforementioned bloody ocean on one of the moons.
With a sealed porthole, all the SM-15 submersible, a neatly designed practical set, offers Simon to navigate is a coordinate sensor and a sluggish X-ray imaging camera to document his findings. Down at the bottom of the sea, Simon captures a photo of a skeleton before he’s pulled back to the surface to have his findings reviewed.
“Iron Lung” is almost entirely set inside of the SM-15, so a lot hinges on Markiplier’s ability to give a leading performance, of which he gets the job done. It’s evident he’s still getting the grips on professional acting, and that’s amplified by the heavily expository script that has Simon theatrically state exactly how he’s feeling, often to the point of obnoxiousness.
Still, it never quite fully feels out of place, as Simon’s exaggerated reaction to being told he’ll have to go back into the hostile ocean to recover a sample of the skeleton is understandable.
But having Simon return into the red sea in the same way contributes to the plot of “Iron Lung” feeling severely backloaded. The front half of the movie mainly serves to set the scene bit by bit, also featuring an excessive amount of close-up shots of sweat or blood dripping.
It’s a long half that doesn’t capture much beyond the path that Simon is on, which isn’t very engaging aside from an engrossing stretch when he must find a way back to the charted territory.
But once “Iron Lung” is past that point, it really begins taking off, and unfortunately, when the extensive spiritual horror of the second half shows itself, none of it is explained. The initial decision to leave the audience in the dark about what’s happening on this moon is one I can respect, but when it comes time for the grander scale of Markiplier’s world to show itself, the decision instead feels like a misstep as the unknown feels more underdeveloped than something able to be discovered.
But the incoherence of what’s happening doesn’t kill the entertainment factor of “Iron Lung,” as the film makes use of its extensive amount of fake blood the film’s production headlines foretold in the amusing, pulp horror climax. Even if the otherworldly events transpiring aren’t quite clear, it’s a joy to look at, so much so that I wish the film contained some of that horror in the first half.
“Iron Lung” is a lot of things — ambitious, incoherent, eccentric, expository — but I do feel a success is one of them. Markiplier succeeded in what he set out to do with a promising debut, even if the grandiose horror of his moon remains underdeveloped.
