Top Alternatives to Subnautica for Windows
Surviving on an Alien Sea
Subnautica is a sandbox or open-world game that is very similar to classics like Minecraft or The Forest. The twist is that the adventure takes place beneath the ocean of an alien planet.
You can download the game from Steam in Early Access format, a sort of developmental demo. Despite its being treated as a "demo", so to speak, you can't download it for free.