Subnautica is an open-world adventure where you explore the ocean on an alien planet after crashlanding. You collect resources and fight creatures to survive. This enables you to establish an underwater base, gain new craft and equipment and explore deeper into the sea. As you do, things get eerie and the game reveals itself to have thrilling horror elements.

Your main objective is to explore the ocean and survive its dangers, while also completing tasks to advance the plot. You collect resources, craft tools, bases, and even submersibles. The largest part of the game is underwater although there are two islands to explore.
You can play in different modes. Survival means you have to deal with depleting health, hunger, thirst and oxygen. You can respawn if you die but lose items. Freedom mode means hunger and thirst are disabled but otherwise like Survival. Hardcore mode means if you die you have to restart from the beginning. Creative mode means that health and thirst are disabled and you also have access to all crafting without the need for resources.
It creates an experience that invites you to dive into an underwater ocean. There’s an open and immersive watery world to discover. Construction is predictably challenging, with air pressure and resources, it's a battle to keep balanced. These housekeeping concerns are as occupying as the daunting, enigmatic and mysterious depths of Subnautica’s world. Although set in the future, Subnautica draws back a curtain on the real underwater worlds we know but can’t explore in a prolonged way.