Subnautica: Below Zero is a 2021 open-world survival adventure developed by Unknown Worlds Entertainment. Set on the icy alien world of Planet 4546B, it follows Robin Ayou as she investigates what happened to her sister while surviving freezing waters, dangerous wildlife, and hostile weather. The game blends exploration, crafting, base building, and story-driven progression, serving as the next chapter in the Subnautica universe with a colder and more narrative-focused setting.