I could easily fall into the trap of overvaluing The Shallows, but by the same token, it would be a real shame to fall into the even bigger trap of overlooking how really, truly wonderful it is as a short, snappy thriller. This is the exact opposite of all the things the phrase "summer movie" typically connotes - it's limited in scope to just one location (and mostly, just one small portion of that location), it has such a small cast that you might just as well call it a one-woman show, it has the basic premise and abbreviated running time of an old-school B-movie - but it's a practically perfect summer movie anyway. The kind that lets you sit in the air conditioning in the dark and be given a good visceral working-over that doesn't leave you any dumber for having watched it, while also not asking you to do any thinking.

That basic premise goes a little something like this: 25-year-old Nancy (Blake Lively), reeling from the death of her mother and starting to seriously doubt her commitment to medical school, takes a trip to the isolated Mexican beach where her mother surfed during her pregnancy. Unfortunately, she arrives at this beach right around the same time that a humpback whale corpse has drifted within a couple hundred yards of shore, bringing with it a large great white shark. Nancy's splashing about attracts the shark, she escapes by crawling atop the whale carcass, and in the process gets a deep laceration on her leg that's guaranteed shark bait. In the immediate vicinity are a small rock outcropping that disappears at high tide, and a buoy, and between these three surfaces, Nancy attempts to stay ahead of the shark while figuring out any way to get back to the beach, or attract the attention of the small number of locals who drift by. And thus does a day and a half or pure misery pass by.

From that, it should be clear that The Shallows lives at the cross between two well-established trends in the horror-thriller tradition: the Implausibly Large & Implacable Killer Shark picture, still going strong 41 years after Jaws, and the much younger population of People Trapped in an Isolated Death Trap movies. Hell, it's not even the first time that the two forms have mixed: Open Water came out all the way back in 2003, though I do not believe that the sharks in that film were the slasher movie behemoths that the CGI monster Nancy faces down is. Anyway, what it lacks in creativity, The Shallows makes up for twice over in confident execution. Not that the bar is terribly hard to clear, but it might even be the best killer shark movie since Jaws itself.

It has its fair share of flaws, some of them fairly minor, some godawfully huge, but what carries it is the fine, taut work of the filmmaking team headed up by director Jaume Collet-Serra, a veteran of multiple Liam Neeson thrillers who hasn't made anything remotely this good before now. The pacing throughout The Shallows is a thing of beauty, as it would almost have to be given that the whole thing takes all of 86 minutes from start to finish (including a healthy chunk of ending credits): there's the nice slow warm-up as Nancy travels to the beach and enjoys an afternoon of surfing, while the movie mounts a multi-front attack to encourage us to anticipate something terrible. There is the matter of the prologue, which makes us aware that a shark and Nancy's broken surfboard will both come into play later, casting a pall over the movie regardless of what else it depicts; but much better and more subtle is the way that Flavio Martínez Labiano's cinematography grows slightly darker and dimmer throughout the first act, while Marco Beltrami's score keeps reintroducing a lightly melancholy tone that cuts against the flashy X-sport editing, music cues and GoPro-tinged camerawork of the surfing action. Everything is working in concert to keep us slightly tense without doing anything specific to push that over. It's a great piece of machinery, readying the viewer for something awful to happen, so that we're already a little jangled by the time that the shark shows up.

The Shallows neatly cleaves itself into three phases: the first part gets us ready for the tightly-coiled waiting game of the second part, as Nancy (and, hopefully, the viewer) is tweaked into a fit of raw nerves anticipating the shark's appearance from out of the gloomy water. The third part is the face-off with the now very present and aggressive shark, which oughtn't work as well as it does; but Collet-Serra is generally very good at keeping the animal visible for short enough bursts that the not-always-convincing CGI is kept from damaging the movie; he leaves just enough longer takes featuring the shark that they could be treated with the time and money necessary to do a convincing job (nobody would call this the best VFX work of 2016, but given the film's budget, it's every bit as impressive if not more than the big comic book bacchanalias).

The film's macro-structure works to give it a constant overall rising tension within an irregular series of spikes of tension vs. relative calm in the course of individual scenes; right up until the point that the shark starts trying to eat the buoy, and the film's jolly ignorance of lamniform biology and behavior starts to become too far off-base even for the needs of plausible impossibility (also, the final showdown between the shark and Nancy is outrageously stupid and boasts the one flat-out terrible shot in the whole movie). But for myself, I found that The Shallows had earned so much good will that the nonsense of the last ten minutes was more in the spirit of good fun than it was materially damaging to the movie's crackerjack thriller construction. It was a film where I spent 40 minutes in a perpetual state of anxiety, doing the whole "put your hands up to your mouth like an elegantly neurotic Victorian lady" and everything. If that's not enough to shoot a movie to the top echelons of summer movie fluff and fun, I don't know what.

Look, The Shallows is good for one thing. It will not reveal secrets of human behavior under stress; it sure as hell won't tell you anything about sharks. Lively's performance is impressively committed and believably tired, with the hair and make-up folks, combined with long, wet shooting days making her look believably thrashed about and damaged, transforming the cheesecake footage of the first half hour into appropriately horrifying tributes to the human body's ability to withstand trauma. But it's not exactly "great acting" in the sense that we typically mean (that being said, I am at least sympathetic to the "my word, Lively can act?!" tendency in the film's criticism, although some of us had already started down that road with The Age of Adaline), more a very striking job of physically daunting behavior and doing it in a way that holds the camera's attention. It's not exactly inhuman filmmaking - our ability to feel for Nancy's predicament is very much a function of our shared humanity with her - but it lacks any real heart, and the attempt to inject some heart into it is the worst trick the film plays. Regardless, the one thing The Shallows does, it does so incredibly well that I'm not in the least inclined to think little of it. A shabby shocker might be what it is, but sometimes a really superlative shabby shocker is exactly what a body needs.