This is the story of Daniel and Susan (Daniel Travis and Blanchard Ryan), a very nice couple who are nevertheless experiencing stress in their relationship. Susan is a TV sports producer who can never seem to turn off her cell phone or unplug her computer. Daniel has somehow managed to convince her to go on a vacation to a tropical location. It should be a fun time, but Susan is unable to relax, while Daniel craves her undivided attention. A growing feeling arises that the two are no longer as close as they once were.

Part of their vacation involves a scuba diving tour. They’ve done it before; no big deal. However, the boat’s guide miscounts the number of passengers who have disembarked and gotten back on. When Susan and Daniel return to the surface, the boat is long gone. They are floating adrift in the ocean with nowhere to go.

At first, it kind of amuses them. Then it turns annoying when the boat doesn’t return. Eventually it becomes terrifying as the hours go by and they realize there’s no help on its way. The couple must contend with dehydration, hunger, and extreme nausea from the rocking of the waves. There are also dangerous creatures bothering them, including jellyfish and sharks. The sharks are perhaps the most frightening of all, as they keep returning in greater numbers. “I can’t stand not knowing what’s underneath me,” Susan frets. As day stretches into night, with no sign of rescue, a massive thunderstorm hits. This is the moment when all the dangers of the ocean come together for one massive pummeling. The situation just gets worse and worse.

Open Water does a masterful job of making you put yourself in the shoes of the characters. It creates a palpable feeling of being helplessly adrift. You often feel like you are floating right alongside Susan and Daniel. Writer-director Chris Kentis (who shot the film with his wife Laura Lau) wisely uses the DV format. Although the picture and sound quality are a bit murky at times, the movie benefits from the immediacy of DV. Because we are all so used to using digital video cameras to record vacations, birthday parties, and other things, the use of DV in Open Water makes it feel much more authentic and lifelike than if it had been shot on conventional 35mm film. (The fact that Kentis threw the actors in with real sharks rather than using special effects also helps.) This feels like some tragic event that was somehow captured on home video, giving the end result a raw sense of terror that is hard to shake off.

I am not often “freaked out” by movies. I see too many of them for that to happen; the conventions of thrillers and horror movies often become repetitive for me. This picture seriously freaked me out, though. Here’s one example: Susan drinks some of the ocean water because she is thirsty. Daniel cautions her not to drink anymore, as the saltwater could cause nausea and diarrhea. Now I don’t know about you, but when I have these things, I like to lay down somewhere comfortable and rest. Daniel and Susan have nowhere to go. There’s no place to lay down. There’s nowhere to rest. There are no pills to take to relieve the symptoms, no doctors to call. In fact, there’s only a continuation of the very things that could cause those symptoms in the first place. Just sitting in the theater making these mental connections freaked me out. I felt tense and frightened inside. It’s too awful to think about. My reaction to the storm scene was really intense, but I don’t know if I can put into words how unnerved I felt during the sequence.

If Open Water was just about being lost or being surrounded by sharks, it would be a good, solid thriller. What makes it an exemplary thriller, however, is that it’s rooted in humanity. You can interpret the theme in many ways – as a parable about man’s insignificance in the face of nature, as a meditation on how we take the comfortable things in our lives for granted, or as a cautionary tale about the dangers of going where people are not necessarily meant to go.

For me though, this is a film about marriage. At the beginning, Daniel and Susan are drifting apart. When they get stranded in the ocean, there is blaming that takes place. Some of the stresses come to the surface. This wouldn’t have happened if her schedule had allowed a different week to take vacation. It wouldn’t have happened if he had listened to her when she said she’d rather go skiing. But the blaming doesn’t last. These two people realize that all they have right now (literally) is each other. They help each other; they take turns being strong for each other when one is afraid. We – in the audience – come to realize that Daniel and Susan love each other and need each other. Certain things might have conspired to put a strain on their relationship, but deep down both know that they can count on the other one. If you subscribe to this interpretation of the film, the ending takes on an even more powerful resonance than it would otherwise.

We’ve all seen lots of movies about “the will to survive” in extreme circumstances. We’ve seen movies about plane crashes and mountain climbing disasters and weather-related emergencies. I would hesitate to say that Open Water celebrates physical survival. The characters are facing a situation that almost guarantees death, unless some sort of miracle occurs (and I wouldn’t dream of telling you whether one occurs or not). Instead, the film is really more about emotional survival. How do you look death in the face and not crumble? How do you cling to the idea that you might somehow be saved? How do you not give up when all evidence tell you that you should? Daniel and Susan look into each other’s eyes and find the answers to those questions.

( 1/2 out of four)

Open Water is rated R for nudity, violence, and language. The running time is 1 hour and 19 minutes.