Well, it's either the heat or the humidity, but something about the Amazon Basin has grabbed "The Emerald Forest" until it's unable to move. This long, wheezy tribute to the Noble Savage has some pretty scenery, but not much else -- it's not a movie, it's a National Geographic special.

The movie claims to be based on "real events and actual characters," which is one way of excusing its clotted improbabilities. Bill Markham (Powers Boothe), an American engineer building a dam for the mighty river, is picnicking with his family on the edge of a clearing when his son is snatched away by Amazonian Indians. Tommy grows up to be Tomme (Charley Boorman), adopted by the chief of the Invisible People; Markham and his wife (Meg Foster) spend the next 10 years looking for him.

The Invisible People talk their own lingo, which is translated by subtitles into italicized, movie-style pidgin. A road is "the River Without Water." When Tomme wants to remember, he says, "I will look through the darkness of what-has-been." The border of the jungle is "the Edge of the World."

What follows are fun facts (40 percent of the world's oxygen is produced by the trees here), helpful survival hints ("When you hear the toucan, danger is near"), illustrations of the tribe's courtship and religious rituals and a clunky action plot that unites father and son against the Fierce People and a bunch of gunrunner/pimps.

Huh, kemosabe! How come in the Room of the Big Picture there are so many Seats-Without-People?

"The Emerald Forest" has some spectacular nature photography that is more to the credit of the nature than the photography -- jaguars in their habitat, achingly green aerial shots and clouds at sunset that look like India ink splattered on a Creamsicle. But the acting is clumsy throughout -- the domestic scenes play like some frowzy episode of "The Addams Family," with Boorman (the director's son) lobotomized and Foster glaring zombie-like and Boothe hulking around, baring his lower teeth and rolling his eyes, like the Hunchback of Notre Dame.

Add to this some equally clumsy action sequences, and some of the worst miniature work anyone's seen since those old '50s horror pictures -- when a dam collapses, it looks like the sides of a bathtub caving in, which is exactly what it is. Director John Boorman intends this mess as a diatribe against encroaching civilization, which is systematically destroying the Indians' quaint customs, like bopping your fiance' on the head with a club or eating human flesh. "They still know what we have forgotten," says the postscript. For example, what cholera feels like.

The Emerald Forest, opening today at area theaters, is rated R and contains considerable nudity, violence and sexual themes.