Kristen Stewart on the creature beat.
Underwater is an oceangoing take on Alien, and why not? The movie isn't a rip-off in the traditional sense—director William Eubank (The Signal) makes no attempt to obscure what he's up to. There's a deep-sea mining base filled with empty corridors that strongly recall the innards of the old space tug Nostromo. There's a wise-cracking crew member, played by T.J. Miller, who's clearly a descendant of the whiny marine played by Bill Paxton ("Game over, man!") in Aliens. And there's a no-nonsense neo-Ripley character, played by Kristen Stewart, who runs around in her underwear quite a bit. The movie is an unabashed embrace of a much better film, but it's not too bad itself.
Eubank gets right down to business. The first thing we see is Stewart's Norah brushing her teeth in a brightly lit lavatory. She's mumbling things ("There's a comfort to cynicism") that suggest a backstory, but who has time for one of those? The base rumbles and shudders, and great gouts of seawater come crashing through the walls. We've previously been informed, during the opening credits, that this command post, situated in the Western Pacific, is located seven miles down in the Mariana Trench, where the water pressure is eight tons per square inch. Chances of survival here would seem iffy.
But a handful of the 316 people on the base do in fact survive, among them Norah, who soon encounters Rodrigo (Mamadou Athie), a black guy who…well, don't get attached. Together, these two come upon another corporate employee, Paul (Miller), half-buried under some soggy debris. (Opening his eyes and beholding the buzz-cut blonde standing over him, he salutes Norah as "my sweet, flat-chested elven creature.") Eventually, the group is enlarged by a pair of lovebird techs (Jessica Henwick and John Gallagher Jr.) and the base commanding officer (Vincent Cassell). And one of the first things they realize is that the facility in which they're currently sloshing around is terminally unstable and will be imploding shortly, and that they are all going to die.
Unless they can somehow make it to a large drilling site not that far away, which may have weathered the recent earthquake, or whatever it was, with less damage. Unfortunately, to get to this haven they'll have to walk—yes, walk—across the ocean floor. (Once they've all donned big bulky white spacesuits and helmets for this trip, the Alien echoes become unmistakable.)
The aqua-monsters that Eubank and his designers have come up with are not as hideous as the Xenomorphs of the Alien franchise, which had an unnerving prosthetic solidity that the digitally confected Underwater creatures can't match. But they've been expensively wrought and are sufficiently nightmarish when we spot them skulking through the murky depths, or chewing on a waterlogged corpse. And in the best 1950s sci-fi tradition, they come bearing a message. As the tech in charge of exposition tells us, they've been summoned up from their gruesome realm deep in the Earth by all the drilling the mining company has been doing. They are the envoys of Mother Nature's wrath. "We took too much," the tech says, "and now she's taking back." Or, as was more concisely said in the '50s, "We're not supposed to be here."