The Vacuum Compartment is a structure in the Tek Tier-building set. it can be placed underwater and allows survivors to live and breathe in it if it's powered by a Tek Generator.
Upon opening the Radial Menu the player will have the option to remove or "freeze" (Makes the side opaque) their selected side. This allows you to create huge rooms that are needed if the player decides to place larger structures within, such as the Tek Teleporter, All actions can be reversed so experimentation is safe.
The walls have little to no collision with structures you wish to place, for example, you can build a Ballista Turret half way on the edge wall, sit on it, spin around until you are outside your base and dismount, however this is a one way trip as you cannot re-mount from the other side. Also, this does not allow the Ballista to be fired outside from the safety of within.
Placing new compartments also has little to no collision, it will ignore Dinosaurs and Structures when snapping onto another compartment.
If surrounding compartments are destroyed, others remaining will stay in place and functional, due to this mechanic it is possible to flood a base if the correct compartments are destroyed.
Anything placed atop of the compartment on the outside will function as if placed out of water, even items such as Campfires will function as usual. This also includes electrical powered structures such as the Refrigerator. While possible, this function serves no real benefit other than allowing turrets to be placed.
While possible to teleport inside an underwater base, any dinosaur too big for the destination will simply be unable to move and have parts of their body sticking out of the base, while it doesn't seem to drain their oxygen nor can they take damage from sources outside the base, it's inadviseable to try to bring anything bigger than you can house.
If your underwater base does not provide the home bonus, it will experience weather events. This is because rain and fog events are not disabled under water. This can be used to irrigate plots.
A variation exists called the Vacuum Compartment Moonpool, which features a downward facing open hatch.
According to some players, it is best to first build the ideal base with whatever preferred materials e.g. 'stone wall/floor, ect'. And then place the Vacuum Compartments over the player's base; therefore covering the entire base structure. A confident player could even build a thatch cabin and perhaps feel fully protected within the Vacuum Compartments.