You have crash-landed on an alien ocean world, and the only way to go is down. Subnautica’s oceans range from sun-drenched shallow coral reefs to treacherous deep-sea trenches, lava fields, and bio-luminescent underwater rivers. Manage your oxygen supply as you explore kelp forests, plateaus, reefs, and winding cave systems. The water teems with life: Some of it is helpful, much of it is harmful.