These insights into anaconda lore come mostly from a character named Sarone, played by Jon Voight as a slimy river rat with a dangerous gleam in his eye. "This river can kill you in a thousand ways,'' he intones, and we get the feeling that he can, too. The propeller of his boat is broken, and he's rescued by a small expedition that hopes to make a documentary about the People of the Mist--a legendary lost Amazon tribe. "I know them,'' Sarone says. "They saved my life.'' And are probably still regretting it.

The leader of the expedition is Terri Flores (Jennifer Lopez, from "Selena"), who will direct the documentary. Ice Cube plays Danny, her cinematographer. Eric Stoltz is Dr. Steven Cale, a scientist. The other members include Jonathan Hyde as their fastidious British narrator, Owen Wilson as the sound man ("Ever notice how the jungle makes you horny?''), Vincent Castellanos as the sinister boat pilot, and Kari Wuhrer as a production assistant. If the cast seems large, reflect that some, perhaps many, of these characters are required so that they can be eaten by snakes.

A movie like "Anaconda'' can easily be dumb and goofy (see "Piranha''). Much depends on the skill of the filmmakers. Here one of the key players is the cinematographer, Bill Butler, who creates a seductive yet somehow sinister jungle atmosphere. The movie looks great, and the visuals and the convincing soundtrack and ominous music make the Amazon into a place with presence and personality: It's not a backdrop, it's an enveloping presence.

The acting is also crucial. Director Luis Llosa, whose "Sniper" (1993) was another good thriller set in the jungle, finds the right notes. He gives the members of the expedition plausible backgrounds (Lopez and Ice Cube say they met in the USC film school), and he allows Jon Voight to take some chances with his performance. Voight's river rat is always on the delectable edge of overacting. He sneers, he frowns, he grimaces, he utters ominous pronouncements ("So young--and yet so lethal,'' he says, as a baby snake sinks its teeth into a fingertip). This is a daring performance: Voight, a serious actor, isn't afraid to pull out the stops as a melodramatic villain, and his final scene, which he plays with a wink, will be remembered wherever great movie exits are treasured.