"Reality is that which, when you stop believing, doesn't go away."
For me the best horror movies were always the ones that focused on the concept of isolation and were set in a location that reinforced that condition. Alien, The Thing, The Abyss... all of these classics of the late 70s/early 80s are benchmarks of this mentality. The “Oh, Crap in the Snow/Space/Water” genre is effectual for a reason- it preys on what we as a social species fear- namely a loss of security when removed from others and a realization that we are not always going to be the apex predator.
It’s this same scenario that gets visited in SOMA. Frictional Games, the developer that created Amnesia: The Dark Descent, offers up a familiar taste of this particular subgenre of horror while managing to keep it from getting stale. Taking place primarily in an underwater facility named PATHOS-II, SOMA drops the protagonist into the environment mostly devoid of any understanding of what is going on and pushes you to explore the surroundings and figure out why this is all happening and just what went wrong in the PATHOS-II facility.