Simplicity is one of the golden rules of horror filmmaking. The more simplistic the premise is, the scarier the movie can be. It’s a rule that 47 Meters Down nails – two women stuck in shark cage at the bottom of a shark infested ocean. It’s such an irresistibly juicy idea that it seems absurd it took them this long to make it. Unfortunately, while the core idea of 47 Meters Down is ingenious, the rest of it isn’t quite as breathtaking.

The film stars Mandy Moore as Lisa, a woman so boring that her boyfriend breaks up with her on the eve of a romantic trip to Mexico. Instead of bagging the trip, she brings her sister Kate (Claire Holt) who is much more interesting. In an attempt to make her boring sister not quite so boring, Kate convinces her to go diving with sharks, which isn’t boring at all. After a quick boat ride with Captain Taylor (Matthew Modine), they soon find themselves in the cage. When the boat’s rusty winch breaks, Lisa and Kate find themselves 47 meters down at the bottom of the ocean, trapped in the cage, surrounded by sharks, and running out of air.

47 Meters Down is at its best when it’s stripped down to its core of survival horror. Director Johannes Roberts has built a film around not one but five prominent fears: claustrophobia, fear of sharks, fear of the ocean, fear of time, and fear of the dark. It’s a premise tailor made for white knuckle tension and yet I found myself at the back in my seat, not the edge of it.

There are a few reasons why the film doesn’t really work, but before we break those down, I want to talk about the few things about 47 Meters Down that are impressive. First and foremost is the underwater camerawork by Mark Silk, which is excellent. The film has some of the best undersea footage I’ve seen and there is plenty of it. That’s because Roberts has made one genius decision with this film – once the girls go under the water, the film stays under the water. There are no cuts to the surface or flashbacks to dry land. The camera stays at the bottom of the ocean. It’s a great way to ratchet up suspense and maintain a brutal sense of claustrophobia. Every frame is filled with blackness where sharks might be lurking. As for the sharks themselves, they actually look great. These are completely computer generated sharks, but they look impressively lifelike and their movements feel natural. They aren’t as present a threat as you might think, but when they do show up, they convey convincing menace.

What isn’t so convincing is the dialog that Moore and Holt are forced to choke down. The script by Roberts and Ernest Riera seems hell-bent on water-logging what should have been a brilliantly efficient thriller with unnecessary backstory and shoehorning weak character development into moments where it doesn’t belong. Watching sisters wax poetic about sibling rivalry while they’re supposed to be terrified that they’re going to run out of air doesn’t add depth to the film, it just adds nonsense. It’s hard to place blame with Holt or Moore with a script like this. Moore is playing a character whose character flaw is being boring, so I suppose she does a good job.

47 Meters Down would actually benefit tremendously from being a silent film. All of the obstacles in the film are physical and most of dialog is simply Kate and Lisa telegraphing what they’re doing or shouting each others’ names, or talking about impressed Lisa’s ex would be. These inane digressions might seem less intrusive if they paid off in any way. Despite all the soul searching that is described in the film, there’s precious little actual character development, and what little there is gets undone by a frustrating third act twist. Without the dialog, the film would really be what it wants – a fierce survival horror movie with an excellent score by tomandandy.

Its not hard to imagine a version of 47 Meters Down that would have been an absolute thrill. The film would be markedly improved by chopping off the entire first act and opening the film going into the cage and focus entirely on the subject at hand. We don’t care about how jealous Lisa is of Kate, we care about the sharks. There’s none of the ruthless efficiency the film desperately needs. The few shark attacks we get to witness are obscured by shaking cameras and fast cuts handheld that feel like the result of corporate neutering meant to keep the film a widely palatable PG-13.

Verdict: 2 out of 5

47 Meters Down is the kind of film that would benefit from a remake. It’s a film with a dynamite premise and an utter inability to deliver on that premise. What we have instead is a tepid, occasionally tense thriller that has no business being as boring as it is, especially at its crisp 89 minute running time. Its a disappointing film in a lot of ways because it gets almost as much right as it does wrong. The sharks are suitably scary and the cinematography is gorgeous. Unfortunately, 47 Meters Down feels like a film meant to play on the Sci-Fi channel or Netflix in the ‘Because you liked Jaws…’ section. If you’re at all intrigued, I’d recommend waiting for Netflix, putting on your favorite scary movie score, and putting the film on mute. It will likely prove a more thrilling watch.