Way better than it was made out to be.
All the detail to the designs, a solid cast and a perfect balance of CGI and practical..all in all really well done. I noticed that there were some edits to the dialogue and I'm guessing this was done to get it that PG-13 rating. An R rated cut or Director's Cut (very unlikely due to the double whammy of it being a bomb and poorly reviewed) would be great. The pacing is superb in the film and I don't feel like it's missing anything necessarily but I'm just curious as to how much more there is/was to Underwater.
If you are a fan of this kind of horror genre (underwater horror) it's nothing you haven't seen before. This film is basically Leviathan meets Deep Rising (with a dash of The Abyss, Alien, Sunshine, Pandorum, Half-Life (PC game) and a few others that I'm sure I'm missing.) The film does a great job of blending excellent practical sets and effects with CGI, is wonderfully shot and all the actors are fine (sans TJ Miller). I think the critics got this one wrong and it unfortunately suffered from poor marketing. The PG-13 rating is pushed the max here and at 95 minutes it moves rather quickly, though it feels like every minute is used appropriately. A nice lazy Sunday flick that really is a B-movie with a big budget. Check it out.
P.S. I noticed that there were a few easter eggs in the film and I'm probably going to watch it again to see what else I may have missed. Spoliers: At the Sheppard Station you will notice that the badge on the captain's old outfit first shows him as a younger man then immediately changes to show him how he currently looks. My guess is they realized this in post-production and were only able make the badge look reasonable in that shot? Also, there are three other characters listed on IMDB that are not present in the film whatsoever. Godmother, Lee and Poseidon Patty...unless Godmother was the voice echoing throughout the facility. Did they end up in the recycle bin?