SubNautica is a relentlessly gorgeous game with an engaging story that gets a hell of a lot less scary from a 'predators' perspective once you find out that as long as you stay on the move and hug the shallows, other than dodging a half-assed bite here or there as you zip around looking for copper / pretty coral samples, nothing will kill you in one shot, or even 2-3 shots. You generally have to be working pretty hard to die to predators. Drowning, on the other hand, is an ever present concern that needs to be deeply respected. After the first few times, you're more angered by your own stupidity that it happened to you and you just lost a backpack full of silver ore rather than actually feeling the existential dread of a death by drowning.
I recommend the 'Neebs Gaming' comedic playthrough for a lighter take on a hefty topic. They did a great job with the voiceovers- so much so that 'Neebs' was offered a voiceover spot in the final version of the game!
I can't account for the sense of absolute terror once you leave the safe shallows, trundle your way out into the deeps in your adorable little micro sub making jetsons noises until you realize you don't have any landmarks nearby, you're surrounded by blackness on every side except for the plankton illuminated by your floodlights, and then you hear the deep, basso groan of something much, much larger than you in the distance. With the occasional hint of writhing coils or jaws that dwarf the scale of your tiny 1 person submersible.
Luckily, you don't *have* to do that at any point in the game. I can 100% confirm you can beat the game without going into the inky black depths that far. That, you have to do by choice.