Subnautica is a survival adventure game developed and published by Unknown Worlds Entertainment. It allows the player to freely explore the ocean on an alien planet, known as planet 4546B, collecting resources to survive.
I know IGN isn't the best, but if that doesn't tickle your fancy, Metacritic will help.
I'm sorry but this is the best survival game ever made, it completely humiliates games like ARK: Survival Evolved, Conan Exiles, and The Forest.
It's perfection, it's sublime, and every single human should play it.
Seriously, stop reading this, buy the game, get it, get it now. It is tantalizing and amazing and wonderful and UGHHHHH OMG so good. Best game of 2018 so far (yeah I know it's February, but we've had some pretty good games so far).
Basically, the reason why the game is so good is because it nails the immersion and the terror (and horror) of being in the ocean, alone.
Couple that with the fact that this is an alien planet with alien creatures that you don't know about, and that just adds more to it.
Even doing something as menial as collecting materials and scanning creatures to learn more about them are fantastic and fun, every little detail was lovingly crafted into this wonderful world.