I will gladly hand it to Open Water: It is a scary movie. This latest triumph of indie ingenuity also deserves some kind of award for achieving maximal gut-level impact with minimal means. Reportedly the moviemaking couple behind the film, writer-director-editor Chris Kentis and producer Laura Lau, managed to create their sumptuously terrifying experience on a tiny budget using only a crew of four, a big wide ocean and two soggy actors. And–oh yeah–a bunch of enormous sharks. The two actors play a scuba-diving couple who get left behind in said ocean; the sharks supply the terror. That’s about all you really need to know about the story; like the digitally shot film’s production scale, it is elegantly spare. But that’s not to say it doesn’t do anything more than scare the bejesus out of you. Afterwards, it also leaves you to ponder various matters–for example the difference, in movies that hope to scare us, between fright and fear.

Fright is the easier tactic, and thus the more frequently used. Indeed, that frequency has meant overuse for far too long. Though I’ve often blamed John Carpenter’s Halloween for unleashing an avalanche of movies that equated “scary” with “knife-wielding maniac lunges out of the dark,” a trend that had reached the point of self-parody well before Scream and Scary Movie, purists may well lay the blame back as far as Hitchcock’s Psycho. It is, in any case, a rare thing in recent cinema to encounter a scary movie that depends far less on fright than fear–an ever-deepening sense of dread that turns every curling wave into a potential source of death.

I don’t mean to suggest that Open Water dispenses with all frissons of shock or surprise. In fact, there are times when a shark’s fin suddenly cuts above the waterline and the effect is not much different than Norman Bates ripping back the shower curtain. But to me such abrupt movements don’t comprise the film’s scariest moments. Real terror comes when the camera is looking down from above the couple and you see a mass of brown move beneath them, lithe and monumental. What’s scary here has little to do with timing or any imminent mayhem, but with our knowledge of the threat’s enormity and, above all, its reality.

The particular way Open Water conjures that reality situates it in the present cinematic moment even as it reveals the extent of the filmmaker’s ingenuity. The crucial context here is that Hollywood’s scary movies now depend heavily on computer generated effects, and Open Water is self-evidently too poor a production to afford even the most rudimentary of those. So when you’re looking at an actress and a 14-foot shark in the same frame, only feet apart, that’s what you’re really seeing. There’s nothing between them. There’s nothing physical keeping the shark from wheeling around and swallowing the actress whole.

That’s what’s scary, and it will be understood–on the most visceral level possible–even by the least film-savvy viewer. It is intrinsically far scarier than any Van Helsing ghoul or computer-designed shark could possibly be. In effect, the success of Open Water stems from an ironic grasp of the current movie zeitgeist. Rather than employing the benefits of the latest fantasy technology, it exploits that technology’s key weakness: that the images it generates sacrifice realism to extravagance. In avoiding costly special effects, the little-horror-movie-that-could appeals to the audience’s suspicion of fakery by embracing the digital era’s new codes of realism.

And that strategy extends to areas like scripting and casting. We see the story’s central couple, Susan (Blanchard Ryan) and Daniel (Daniel Travis), only once before they head off on vacation, and though this scene comprises only a few camera set-ups and sparse dialogue, it’s incredibly rich. The characters evidently are married, have no kids and work high-pressure jobs; both are hooked into their cell phones more than into each other. There’s an undercurrent of friction beneath their efforts to shut down their lives and leave town for a few days; no question about it, both need this vacation.

Both at home and later when the couple reach their tropical destination, all geographic specificity is avoided. Not so cultural specificity, though. These characters belong to the great American professional class, and as such, they are brilliantly evoked. One of the shrewdest things about the film is its use of actors who seem like they could have stepped out of a Sears catalogue, or more likely, off the casting stage of a reality-TV show. Granted, the filmmakers could have not found, at any price, stars who would have spent days in the water with real sharks. But what a clever choice they made in casting performers whose blond, wholesome, entirely generic good looks make them seem so blandly “real.”

More points for shrewdness accrue the night after Susan and Daniel arrive in port to await their dive. Here again, the dramatic approach is sharp but utterly simple. In bed, they continue talking about the hassles they’ve eluded to reach vacation; a residue of their earlier tension lingers. They playfully wrestle with the possibility of making love, but she declines. It would be too much, of course, to say that what happens to them the next day is some kind of exteriorization of the unaddressed problems in their relationship. On the other hand, after emerging from the movie you might ponder whether its central crisis would be so gripping if the two main characters had been a couple of guys who just met before the dive. Obviously not. We’re engrossed by this couple because of the intimacy, vulnerability and connectedness evoked in the night-before scene.

Evidently experienced divers, they go to sea on an excursion boat containing a couple of dozen tourists with their diving gear–except for one guy who lacks both a partner and full gear. It’s due to the confusion he causes that the boat’s crew thinks it has picked up all the divers when it hasn’t. Daniel and Susan bob to the surface miles from land with their boat rapidly becoming a speck on the horizon.

Roughly half the movie is left to go, and I’m not about to spoil the surprises to come. But certain non-revealing things can and should be said. First, Kentis’ scripting subtlety remains intact throughout. The challenge facing the writer-director after Susan and Daniel are left behind–and the movie begins to earn its title in spades–is akin to, “OK, make a movie with just two characters in a bare, locked room.” What to do? When I thought back on the film afterwards, I could only marvel at what Kentis didn’t do. There are so many little cutesy games and melodramatic tricks that any filmmaker would be tempted to pull to milk the situation and hold the audience’s interest. Here, the very few of those that appear at all are underplayed to a fault. Mostly, we are left with a big ocean and two very soggy and increasingly anxious people who can’t believe what’s happening to them (as in, who could?).

Second, Open Water joins two other low-budget indie films–Linklater’s Before Sunset and the upcoming Maria Full of Grace–as the most intelligently and scrupulously made American movies of the year. Scene by scene, above water and below, Kentis renders his ever-more-harrowing drama with amazing precision and economy; not a shot is wasted, not a frame less than optimally composed. Considering the minuscule budget and the perilous, hard-to-control shooting conditions, this thoroughgoing virtuosity is more than impressive–it’s downright astonishing.

One area where some viewers might raise aesthetic objections is the film’s digital look, which yields a low-grade, cheap-looking image. I understand folks who are tired of this look; indeed, there have been plenty of occasions in the past couple years when I’ve wished the latest no-budget wonder could have afforded film stock.

No question about it, celluloid generally looks better. (Though some recent digital movies appear virtually indistinguishable from film, Open Water is of the obvious, cruddy-looking variety.) Yet I’ve also heard the argument that the lack of visual resolution here actually increases the suspense, since there are times when you simply can’t tell a wave from a shark’s fin. There’s obviously some truth to that; your call.

Speaking of those fins, I have so far avoided discussing the critical action of Open Water and its undersea instigators because there isn’t much you can say about these sharks except that they are absolutely horrifying on every level you care to name, including the symbolic. Like the iceberg in Titanic and the dark woods in Blair Witch Project, they offer an implacable emblem of nature and the powers that man naively imagines he vanquished with the baubles and distractions of technological modernity.

How did the filmmakers manage to have sharks and humans “acting” within touching distance of each other, with nothing to shield the tender species? The film’s press notes say there are such things as shark wranglers in the Bahamas, who guided the sharks toward the actors by tossing chunks of tuna near the humans. The sharks are supposedly used to people and won’t attack as long as they get their tuna.

This strikes me as one of the craziest things I’ve ever heard. Is it possibly true? Who knows? All I know is that thinking about the making of Open Water scares me as much as thinking about what’s in the story. In a movie that trades so ingenuously in fear, I suppose that’s a compliment. x