Two sisters vacationing in Mexico (Mandy Moore & Claire Holt) sign up for a dip into a creaky shark cage hung from a decrepit party boat.

I don’t think, in a movie titled 47 Meters Down, that it would be considered a spoiler to tell you that something rusty snaps and they plunge to the bottom, which is at a depth of, oh never mind. They have an hour of air, and only spotty radio communication with the boat.

Not great, but focused and generates good tension, backed up with some genuine jump scares, if that’s what floats your shark cage.

A claustrophobic movie of desperation that would have benefitted from a little characterization. (89 min)