Even without ''Jaws''' teeth-gnashing great white, ''Open Water'' is just as likely as the 1975 classic to keep you planted on dry land. Loosely based on a true story about a couple abandoned by their tour group off the coast of Australia, this independently financed thriller (in select theaters now) has critics hooked (EW called it ''startlingly intense''). Here are a few reasons why this little indie could reel in big audiences when it opens nationwide Aug. 20 -- and the one way it tops Spielberg's seminal shark thriller (hint: in this movie, the bad guys aren't battery-operated).
IT MIGHT HAVE HAPPENED The 1998 disappearance of scuba-diving tourists Tom and Eileen Lonergan off the Great Barrier Reef inspired writer-director Chris Kentis to explore what may have happened to them. As a certified scuba diver, Kentis knew that sharks rarely kill humans. But during his research for ''Open Water,'' he discovered exceptions. ''Even the sharks considered dangerous to humans usually only bite out of mistaken identity. But as dehydration and exhaustion set in and people's heart rates change, they start resembling a primary food source for sharks: wounded animals. So it's only a matter of time before they do close in.''
THE SHARKS ARE REAL When a fin pops into frame, don't squint to see if there's a prop guy holding it up: There are no faux creatures or computer-generated shots in this movie. ''It was always a part of the plan, regardless of budget, to use real sharks,'' says Kentis. ''As divers, we knew we could get the footage, and it just made sense.''
Shooting with real sharks required stars Daniel Travis and Blanchard Ryan to wear chain mail under their wetsuits and avoid splashing or kicking, which could excite the sharks. On the bright side, the finned friends inspired great Method acting. ''When we pulled the boat up and 45 or 50 sharks appeared before we'd even put tuna in the water, I had that initial moment of 'Oooh-kay,''' Travis admits.
THE MOVIE TAKES A LESS-IS-MORE PHILOSOPHY While the sharks are definitely terrifying, ''Open Water'' really scares the bejesus out of viewers by limiting sightings of the toothy costars to crucial moments. To that end, only two days of shooting were dedicated to the sharks. ''Sometimes what you DON'T see is really the scariest thing in a movie,'' Travis says.
THE CAST AND CREW WERE COMMITTED Well, they didn't really have a choice -- shooting lasted 8 to 10 hours a day. ''I lost my equilibrium. I'd walk off the boat like a drunken sailor at the end of the day,'' says Travis, noting that producer Laura Lau was seasick for much of the time. Travis and Kentis were also stung by jellyfish during filming. Ryan had other problems: ''We didn't know she had a fear of sharks until 20 minutes before the boat left the dock,'' remembers Kentis.
Although Ryan was able to control her terror, she was later munched on by another predator: a barracuda. ''That was by far the scariest moment,'' says Kentis, who dropped his camera to help her. ''And she kept saying, 'Did you get the shot?' And of course I didn't, so it was just a bad day all around.'' But it was Kentis who came the closest to becoming fish food: To get a close-up of a shark, he climbed into a baited underwater cage. ''The shark barreled right into the cage, which was kind of like being stuck in a small elevator with a big shark,'' says Kentis, who, using his camera, was able to push the creature's head into a corner of the cage and escape unharmed.
IT'S NOT JUST ABOUT SHARKS ''This was about taking two characters who are used to being in control and putting them in a situation where they have no control whatsoever,'' says Kentis. ''Their fear has to do with abandonment and that loss.'' Keeping the sharks off screen for part of the movie only emphasizes the horror of the couple's complete isolation. ''When you're 20 miles out and you put your mask on and look into the abyss below you and there's just nothing, you feel your insignificance.''