On Underwater - there was stuff about it I liked, but it also fell a bit flat for me unfortunately. Creature stuff was pretty cool, I liked the look of the movie, but it never amounted to more than just its various parts. And I really don't buy the apparent Lovecraftian connections that were being touted after the movie released. There were parts of the movie that were pretty fun though.
As far as recent Alien knockoffs go, I preferred Life. I'm always down for more fish monster movies, though, so here's hoping the Aquaman spinoff about the Trench comes to pass.