200 yards off shore that you can only see at low tide. Will Nancy need that rock when the shark strands her in the water? Will studios continue to charge top dollar for tickets to movies that strain credulity to the snapping point?
The rest of the movie shows Nancy and the shark dueling for dominance. Given her medical training, our heroine can turn a wet suit into a tourniquet or use her necklace to stitch up a nasty gash. As Nancy waits for a rescue, she pours out her feelings to a wounded seagull who seems to represent her dead mom. ( I'm figuring the shark is a symbolic warning not to quit school.) It's all patently ridiculous. But Collet-Serra and Lively show no mercy in hooking us with the B-movie tension. And we bite.