Iron Lung

The player controls a silent protagonist that pilots a midget submarine. Gameplay is set entirely within the one-room submarine, with little room to move. The submarine is controlled using its navigational equipment at the front. The submarine's heading and position are displayed with a minimalist interface. The submarine lacks any viewing ports, and the player cannot exit it, forcing them to use their map and the submarine's camera to navigate the game map. At certain points, the player must use the submarine camera to capture photographs, which reveal surroundings and details about the area the player is in. Events occur throughout the game, including scripted decreases in oxygen and pressure which do not affect gameplay.

In a future where humanity has colonized space, an event known as "The Quiet Rapture" causes all stars and habitable planets in the universe to inexplicably disappear, leaving only individuals aboard space stations or starships alive. To secure the survival of humanity, the Consolidation of Iron (COI) launches an expedition to AT-5, a desolate moon that has recently formed an expansive ocean of human blood, believed to hold vital resources desperately required to sustain human life. The player character is a convict sent to navigate the trenches of the blood ocean in a small submarine known officially as SM-13, nicknamed the "Iron Lung", to verify the existence of the resources. Due to the pressure and depth of the ocean, the main hatch is welded shut, the forward viewport has been encased in metal, and communications are lost shortly after submerging. The player is promised freedom upon their return to the surface, but a note left by a previous occupant of the submarine warns them otherwise.

The player takes control of the Iron Lung as they navigate through the treacherous, narrow caves and trenches. Using the submarine's camera, they capture photographs of points of interest scattered around the map. However, the photographs reveal increasingly unusual features such as plant growth, rock formations which defy explanation, large unidentified skeletons, and artificial structures resembling building facades. The player must also contend with a fire which breaks out in the rear of the submarine. As the Iron Lung draws closer to one point of interest, an orb of light, the vessel begins to shake violently. At another point, the player captures the eye of a large, unidentified sea creature, which then attacks the Iron Lung in retaliation, causing a significant leak. After reaching the final point of interest, as the player attempts to reach the camera controls, the creature breaches the submarine, ending the game and returning the player to the title screen.