In Other Waters is a little game about a xenobiologist named Ellery Vas exploring an alien sea, and finding it (unexpectedly) teeming with life. You don't play the biologist, you play an artificial intelligence powering and controlling her advanced diving suit, but you are essential in helping Ellery to observe and classify these new species, to collect specimens, and to navigate the seabed. Despite what sound like similarities, In Other Waters is, as Nate pointed out, definitely not Subnautica.
It is really very good, though. It's very meditative. Calming. It's possibly exactly what you need right now.