We fear what hunts us. That is why we fear the shark.

And that is why a ticky-tacky no-namer like "Deep Blue Sea" can still now and then give us a goose so intense we rise from our seats, borne aloft by a spike of pure terror, and scrabble at the air as if there is safety in height if only we could flap our arms fast enough.

It has several great moments when a Paleozoic eating machine erupts from the deep, jaws akimbo, teeth unsheathed, snatches up a piece of screaming human sushi, and plunges backward into the big wet, its wiggling lunch trailing clouds of blood like a Messerschmitt just smoked by a Mustang.

Cool. I like it when the shark eats the people.

Alas, the weakness in the movie is what happens between these frequent but not frequent enough tete-a-teeths. That is when the actors act, the director directs, the set designer set-designs and on and on.

The movie was--well, directed is too grand a word--"engineered" by Renny Harlin, who has a number of big, mechanistic thrillers to his credit, most of them starring his ex-wife Geena Davis, like "The Long Kiss Goodnight" and "Cutthroat Island," but with "Die Hard 2" and "Cliffhanger" thrown in, too. He also has the dreadful Andrew Dice Clay film "The Adventures of Ford Fairlane" to his credit. You can guess from that resume he's pretty good when things happen fast and not much good when characters talk slow--or at all.

The setting is a structure more akin to a space station than to an oceanic environment. It's a tubular construction with many different levels, complete with picture windows, a kitchen, elevators, creaking doors, rivets, sweating pipes, radio rooms. Of course it has a surface level (helpful for the inevitable helicopter explosion, a gassy Armageddon of napalm). But so much of it is underwater that when it develops leaks and the tubes are half filled, the big monsters can slither through the liquid, their cruising dorsals touching off deep vibrations from the collective subconscious about fear of being eaten; then, just as suddenly, they pop out and take prey at key moments.

The best of these occurs when a fellow stands up and gives a nice loud talk about leadership, like Knute Rockne. He wants to win one for the human race, but it's the ripper who wins, taking him in a single satisfying crunch. So much for grandstanding actors (it's every movie critic's secret dream, I suppose).

This structure is peopled by largely anonymous and under-talented actors (Stellan Skarsgard has the good sense to get himself eaten very quickly so he can get back to his serious work). The star is Saffron Burrows. I'm just wild about Saffron--I love that vapid Euro-model look--but does anybody know who the hell she is? Then there's Thomas Jane as the shark wrangler. Does he also edit big books about planes and ships? Nobody around here seems to know. Only Samuel L. Jackson and LL Cool J are recognizable. The rest are mere bait, some of whom are eaten early and some late. Some bleed, some merely wiggle and scream.

They allegedly represent some sort of medical research team. They have been--the science here is a little shaky--genetically mutating the sharks to increase their brain size to produce a protein that will cure Alzheimer's. But this means the sharks have not merely grown bigger but gotten smarter as well. In other words, you have a movie in which sharks with triple-digit IQs hunt humans with double-digit IQs. It's no contest.

And it's not much of a movie. "Jaws" is the inevitable comparison, but it's closer in spirit to "Alien" or even the great old Howard Hawks classic "The Thing," in which a vegetable man from outer space ate Air Force officers and liberal scientists who tried to communicate with it.

That's one cliche that the movie avoids. No one tries to make peace with these 40-foot biters. But that's the only one.

Deep Blue Sea (105 minutes, at area theaters) is rated R for violence humans would consider shocking but sharks would view as a trip to McDonald's for Happy Meals.