You are mostly defenseless, having only weapons that can stun or rappel creatures for a short time as opposed to anything lethal which makes the dangerous “leviathan class” predators terrifying.

Many describe this as an unintentional horror game due to the feelings of uneasiness and sometimes straight up terror many people feel. During their time on the planet, the player must content with various forms of hostile alien predators which range from minor issues to submarine-destroying monstrosities to be avoided at all costs. Its a beautiful story told indirectly in a masterful way, having the player uncover it at their own pace through exploration. Using materials gathered from the world and salvaged from the wreck of the spaceship you were aboard, you must try to survive, develop your arsenal of technology, and start to uncover the mystery behind how your ship ended up where it is.

A sci fi survival/exploration game in which you play as an extremely unlucky astronaut marooned in an ocean on a hostile alien planet.

Subnautica game faq