Sunil’s review published on Letterboxd:
I added William Eubank's previous two films to my streaming queues on the way to my car after seeing Underwater. If that's not an endorsement, what is? What makes Underwater interesting and cool is also what's likely disappointing audiences: the primary antagonist of this film is not scary monsters, it's BEING UNDERWATER. It wastes no goddamn time, immediately killing hundreds of unseen crew members in a disaster of unknown origin and setting up a goal for the survivors. All they have to do is cross the ocean floor to another station so they can escape. Yes, they do eventually encounter some scary monsters, but they're almost afterthoughts compared to everything else they have to do to survive. Everyone keeps invoking Alien, but the more apt comparisons would be Cloverfield and The Descent, survival stories where the environment and surroundings are the danger and the monster is rarely seen and certainly not the primary focus. It's the kind of movie where each character essentially has one character trait and maybe one poignant piece of backstory and the actor does the rest of the work, and that's fine, especially with a steely Kristen Stewart at the helm. Most of all, this movie just looks fucking great; it's got a huge-ass budget for a film dumped in January and it shows. Did they film this whole movie underwater? Who knows, I sure can't tell. The creatures look cool, and they're just comprehensible enough, finding the right balance between "oh shit what was that" and "I can't see a goddamn thing." Things get murky seven miles deep. Underwater is stylish and fun, more of a sci-fi thriller than a horror movie, and it maintains a healthy amount of tension for most of its runtime, steadily building toward a rewarding third act.