(CNN) —  

Summer and sharks have proven to be a pretty potent combination, which is the main draw in “47 Meters Down,” an old-fashioned “B” movie that offers its share of reasonably effective thrills, even if it gets predictably light-headed long before its over.

The producers (among them Harvey and Bob Weinstein, who made the movie and then sold off the rights) caught something of a break in casting Mandy Moore in this low-budget genre flick before “This is Us” became TV’s new darling. Granted, it’s a role saddled with a lot of shrieking, panting and bad dialogue (even the movie’s hashtag is #Sharkbait), but with any luck there will be more parts coming that the actress can actually sink her teeth into.

Frankly, director/co-writer Johannes Roberts would have benefited from devoting a little more of the movie’s 89-minute running time to introducing the characters, and a tad less to fabricating increasingly dumb ways to tease out the protagonists’ predicament, especially with the air in their tanks creating a built-in expiration point.

Moore and Claire Holt (CW’s “The Originals”) play sisters Lisa and Kate, respectively, just a couple of bachelorettes in paradise on a vacation in Mexico. Lisa, however, confesses that she’s just broken up with her boyfriend, prompting her more free-spirited sister to coax her to get out and live a little.

The two meet a couple of guys, who talk them into a shark-cage excursion with a somewhat shady-looking captain (Matthew Modine). “It’s like going to the zoo, except you’re in the cage,” they’re assured.

Alas, something goes terribly wrong, and the sisters are left trapped at the ocean bottom, running low on air, with massive great whites in the water. Thanks to full-faced masks, the two can still communicate, although that’s as much a curse for the audience, given the level of the writing, as it is a boon for them.

The movie’s saving grace is the visceral response that sharks produce, even more than four decades after “Jaws” first had audiences screaming. It’s no accident that Discovery Channel’s “Shark Week” is an annual event.

For all the wrinkles and riffs in between, that sense of helplessness remains a powerful, tension-filled hook, even if Roberts has to jerk the audience around more than a bit to keep them dangling. As for the groan-inducing lines, for some those chuckles will simply provide a welcome breather.

All told, “47 Meters Down” delivers enough rudimentary bait to justify this sort of low-budget exercise. If nothing else, it’s also a reminder that in the realm of thrillers, the boring stick-in-the-mud personality is usually the one with the right idea.

“47 Meters Down” premieres June 16 in the U.S. It’s rated PG-13.