Lisa and Kate (Mandy Moore and Claire Holt, respectively) are sisters on vacation in Mexico, who make the ill-advised choice to go on a cage dive with a couple hot Mexican guys. See, the guys have a buddy with a rickety boat that will motor them out to a ripe spot, fill the water with chum, rent the ladies some scuba gear, and drop them in a cage to get an up-close look at great white sharks. I mean, what could really go wrong?
Snap! goes the winch cable, and the cage and women go plummeting 47 Meters Down into the shark-infested darkness until they hit the sea floor with a thunk. To make matters worse, they are just out of range of communicating with the boat, AND they are low on air, AND their cage is wedged shut in the fall. Even if they were able to swim to the surface quickly from that depth, they'd get the bends and die. What is one to do?
There are some intrinsically, frustratingly dumb things in this film. To start with, the characters are having full conversations with each other. Sure, their masks are large and their whole face is in there, but their ears are full-on out in the water. Can you hear through your face? Maybe they are lucky that they can't hear through their faces, because the script is terrible. Now, I don't except a highbrow screenplay, by any means, but when Mandy Moore shrieks to her sister, "It almost got me!!!" you whisper encouragingly under your breath, "Next time, shark... Next time..."
To its credit, 47 Meters Down plays upon the sheer claustrophobia of deep-sea blackness (where no one can hear you scream). At one point, the beam of a flashlight just shows bits of illuminated floating fuzz, like driving through light snow at night. You find that, like the characters, you are of course looking really hard into the darkness, which makes the sudden appearance of a big snappy monster that much scarier.
There is some expectedly pleasing big bloody payoff in the finale—though if 47 Meters Down were daring and just, it really should have ended 5 minutes before it did. Sometimes you really just want the sharks to win!