[NO SPOILERS]
If you're a sci-fi horror fan, then you'll likely enjoy this one. Kristen Stewart fits the role really well & though I've never been a fan of her before, I definitely am now thanks to her great acting in this film.
This movie is unique in it's own way, & is a really engaging film for people who eat up dark, tense sci-fi. We need more sci-fi horror set on alien planets, or on the more alien parts of earth like deep underwater such as this one. For that fact alone of how lacking the sci-fi horror genre has been the last few years, this is refreshingly welcome & stands out as it's own film. It really scratches the itch you didn't quite know you had!
This film isn't for people who like deep psychological thrillers that have a long boring build-up with zero action, or extreme gore horror fans, or for people who enjoy cheesy action as this film is none of those things. It's a simple, well-acted dark, creepy sci-fi with a good balance of action, tension & lore (I won't spoil what kind of lore though as that's upto the watcher to decide).
4/5 stars as I am biased towards adoring sci-fi horror, otherwise I'd give it a 3.5/5 for people who are more picky with these kinds of films.