I've heard a lot of good things about subnautica too.
It is very good. Definitely one of my favorite games ever. I won't say much because of spoilers but going through and learning about the planet and solving the various mysteries is amazing.
Below Zero just had a major update and I almost broke my rule and fired it up, haha. But I want to be able to do the story all at once without waiting for updates, so I resisted.