Great watch, will watch again, and do recommend.
To be fair, I was sick when I saw this was available and couldn't resist watching it.
I'm a fan of Kristen Stewart (most of the time), and sure, she runs around in her underwear for a lot of the movie, but that's not a reason to watch the movie, it's a horrible reason for a web search.
A great reason to watch this is that it is a underwater survival story. The isolation and technical strategy involved in dealing with this situation makes it gravely atmospheric, without the threat of "monsters". Honestly, that version would have also made a great movie.
The movie clearly takes queues from several other great movies, and while it does it very well, the problem there is "several". Had the movie mirrored only "Alien", it probably would had been a stronger story. Clearly the writers wanted the threat to build, similar to video games, or possibly more similar to an alien invasion movie.
The cross between a survival / slasher movie and an invasion movie muddles the feel of the movie somewhat. It downgrades the movie from truly excellent to great, and I don't feel that everyone is going to get the proper experience to recognize all of the great individual parts because the overall pie tastes a little funny.