Norah is a mechanical engineer aboard a large structure surrounding the Kepler ocean drill, which is in the business of penetrating the Earth’s crust searching for minerals like a hungry anteater. She’s a cynical sort of savior, scooping spiders from the sink, but she knows how to make the tough decisions too. When the structure is rocked by several massive jolts, she’s forced to sacrifice a couple of colleagues while sealing off a passageway to save the whole ship. Soon it’s just a small group of survivors, hoping to make their way down to the ocean floor and across to another drilling station, the Roebuck. It seems their vulnerable suits and the deadly pressure from the miles of water they’re under will be the most dangerous thing to navigate, but they’re of course underestimating the real threats of what lie beneath.
Written by Brian Duffield and Adam Cozad, the specter of “Alien” haunts “Underwater,” a damp riff off and tribute to the 1979 extraterrestrial horror thriller. But it hews so closely one can easily predict each story beat, each reveal, each jump scare. Director William Eubank distinguishes the formulaic film with a jittery artfulness rendered in shades of gray and green, but what elevates the B-movie is the presence of Stewart, who is both a movie star and a great actress. Although she sometimes seems to vacillate between the two poles (“Charlie’s Angels” vs. “Personal Shopper,” for example), in “Underwater,” she is both, bringing her cool élan to this monster movie under the sea.