Although, actually, I rather enjoyed William Eubank's 2020 science fiction action horror movie. But it doesn't really work, and I was curious why. Spoilers follow.
It's essentially Alien underwater. A deepwater drilling platform located (improbably enough) at the bottom of the Mariana Trench is hit by what seems at first an earthquake. Kristen Stewart and other highly attractive underwater drilling technicians, as all commercial drilling technicians of course are, run around the collapsing facility in their underwear, closing bulkheads and pressing control panel buttons and so on. Some of them are killed in the chaos. The survivors clamber into diving suits and make their way across the seabed to a different part of the facility, where the escape pods are located. More of them die, this time hauled away by tentacled monsters—hitherto-unencountered lifeforms, mansized pallid motile globs of feelers and teeth. As the facility further collapses more of the cast are, as per Alien, snaffled by these nameless horrors. There is much wriggling through collapsed, flooding corridors, and plenty of shock moments, diving suit helmets suddenly filling with blood as their wearers howl and so on.
Finally Stewart, Jessica Henwick and John Gallagher make it to the escape pod room, all the slightly less attractive cast members having been tentacled-away. Stewart manages to send Henwick and Gallagher away in their pods, but her own pod is broken, so she stays behind. And this is where the movie stages its big reveal. The human-sized undersea monsters are merely the progeny of one absolutely gigantic tentacle-and-teeth monster
Far, far beneath in the abysmal sea,... and it's Cthulhu! It's your actual gigantic Lovecraftian beast. Stewart gazes into the ph'nglui mglw'nafh r'lyeh wgah'nagl fhtagnian horror for a while, and then presses the base's nuclear self-destruct (all mining platforms, as I understand it, are equipped with one such) immolating herself and the elder horror both at once.
From ancient, dreamless, uninvaded sleep
The Kraken waketh



