In The Shallows, Blake Lively plays Nancy, an American med student on a surfing vacation to a remote beach in Mexico. While surfing, she is attacked by a shark, and injured. Somehow, she has to get back to shore in one already-munched-on piece. It’s a woman-in-peril movie, a movie about surviving a desperately hostile situation. It’s pretty well-done; kinda exciting. I know, tepid praise. And I’m not sure why I can’t recommend it with more enthusiasm. Lively’s a fine actress, she does good work here, and we do genuinely worry that she may not survive. It’s not that we’re indifferent to her plight.

This is going to sound weird, but the movie it really reminded me of was Gravity. That was in outer space, while this is a shark-infested lagoon, but otherwise, they’re basically the same movie. In Gravity, Sandra Bullock is stranded, and in danger, but she also has a series of steps she can take. She has to get from the space station to another space station to a satellite array to another facility; that’s what drove the plot. She has to get from damaged space haven A to damaged space facility B, to C and D and E and eventually back to Earth. Same thing here. Lively sees a dead whale in the lagoon–presumably, the whale is what attracted the shark. So Lively climbs up on the whale, and that keeps her safe for awhile. But not for long; sharks apparently can ram dead whales, to knock people off them. So Lively has to escape to a coral reef. And from there to another one. And from there to a buoy. It’s the same plot. “I’m safe for now, here, but that won’t last. I have to get to there. And from there to that other place.” And so on.

Of course, throughout the whole awful ordeal, Nancy’s resourcefulness, imagination, and courage pull her through. She doesn’t have much to work with, and she has a nasty, deep shark-bite wound on her thigh. But she’s a medical student; she does know how to suture a wound, for example. Of course, all she has to work with are her own earrings, but in a pinch, they hold up adequately. She turns her wetsuit jacket into a compression bandage, and uses what’s left of her surfboard for shade from the brutal tropical sun. All those scenes are fascinating, well acted; they’re the best things in the movie.

I compared The Shallows to Gravity, which it very closely resembles. But the biggest difference is that Gravity was tremendously exciting, absolutely riveting every second of the way. I found The Shallows kind of meh. I’m trying to figure out why. It’s not the star–Blake Lively is terrific in this, every bit as interesting as Sandra Bullock was in her movie.

I think there are two reasons. The first is just the setting. We don’t know much about space, but we do know it’s plenty dangerous. And we find Sandra Bullock’s resourcefulness convincing, because we don’t know better–we don’t know anything about outer-space survival. But we’ve all seen how many scary shark movies? And how many hours of Shark Week on TV? Ultimately, I think, the last third of The Shallows doesn’t work very well because we think we know how actual sharks actually behave, and it’s not the way this shark behaves. If real sharks can’t do what this shark does, then her duel of wits with it is substantially diminished.

I think there’s another reason too. In Gravity, George Clooney’s character dies pretty early on. That heightens the stakes; we think that Sandra Bullock’s character might actually die. Of course, she’s not going to die; Hollywood doesn’t do that to protagonists–only second leads. But in this movie, Blake Lively plays essentially the only character that matters. There are two Mexican dude surfers in it, and they do get shark-eaten, but they don’t matter as characters–we never even learn their names. So their deaths don’t have much resonance. And that means, we never really do believe that Nancy might not make it.

My all-time favorite shark movie, Open Water, a wonderfully terrifying small indie movie works precisely because we don’t really have any reassurance that the characters are going to survive. As we watch, we think that they’re as likely to die as to live; it generated terrific suspense throughout for that very reason. I wonder how much of the difference is due to casting. Open Water starred Who? and Whosat? (Blanchard Ryan and Daniel Travis, actually). While this is clearly a Blake Lively vehicle. She’s probably going to survive it.

Anyway, if you’re in the mood for a pretty well made, moderately suspenseful, fairly exciting woman-in-peril movie, The Shallows does deliver. There’s a lot to like here; I can’t point to any part of the filmmaking that didn’t work. It’s just a little too easy to compare it to other really similar movies that are just that much better.