It's not that hard to figure out why sharks are so fascinating. The menace, the sense of danger in an already alien element, the helplessness in the face of an arbitrary terror that is unyielding and pitiless -- sharks make great metaphors for God or destiny or whatever hapless fate awaits the unwary. The cold black unblinking eye, the razor teeth, the silent gliding motion, the voracious appetite (this, after all, is an animal that is known to practice intrauterine cannibalism): Sharks are the stuff of nightmares -- unbelievably bankable nightmares at that, as the "Jaws" phenomenon demonstrated. If sharks didn't exist, we would have to invent them.

Unfortunately, the National Geographic Society special, "The Sharks" (tonight at 8 on channels 26 and 32), does its best to take all the the terror out of sharks, trying desperately to convince us that the dear creatures have been the victims of calumny and slander. In trying to induce our sympathy and substitute pity for the much more interesting emotion of terror, the writers of this special end up stripping the sharks of half their fascination. Sharks, it seems, are misunderstood, put-upon creatures in desperate need of a public relations overhaul, "the only creature that still inspires a universal unreasoning fear." One would think that that was accomplishment enough in an age that proffers more than enough sources of perfectly reasonable fear from which to choose. But instead of exploring the sources of the terror, and the history behind the fascination with this ageless, timeless creature, the documentary spends a lot of time making banal comparisons, reducing the fearsome to the familiar. We learn that we are in more danger of dying in a traffic accident than from a shark bite, for instance, a fact that can be considered comforting only if you happen to spend as much time on the high seas as you do on the corner of Connecticut and K.

Still, the photography is magnificent. There are rare glimpses of the whale shark, the largest fish in the ocean; shots of deep-water sharks, black and eerily exotic, with huge,pale-blue, luminescent eyes; the streamlined elegance of the great white shark, the white death, moving with a pitiless grace, beauty being never very far away from terror. For a finale there is a stunning sequence of the birth of a shark, emerging from its egg case, alone and tiny in the vast ocean and already prepared to devour anything smaller than itself.

Some of the myths perpetuated about sharks in the past are replaced by even more intriguing facts -- at least some species of sharks, it turns out, are not the perpetual-motion machines it was once thought they had to be to survive, but instead can be found off the coast of Mexico, resting for hours at a time in a shark's version of an opium den -- underwater caves where the high oxygen content may have a narcotic effect that renders the sharks immobile while they are cleaned of parasites by the industrious remorae, the small attendant fish that attach themselves to the body of the shark.

Unfortunately, the quality of the script is not equal to the beauty of the photography, a fact that is exacerbated by the monotone in which narrator Alexander Scourby chooses to deliver it. The latter half of the show is taken up with more than you ever wanted to know about the shark industry in Japan -- lots of shots of dead sharks in the fish markets, cooked shark between the chopsticks, not to mention the various shark portions that have been chopped, minced, tanned and encapsulated for a variety of purposes. It is boredom, not pity, that such scenes inspire; the show does much better when it excites admiration for a 350 million-year-old creature that evolved before the dinosaurs and has remained virtually unchanged over time.

Still after an hour of "The Sharks," the basic reaction remains unchanged; a perfect gauge being provided by the admirable shark expert Eugenie Clark, who at one point remarks that if you happen to run into a shark, "You should think, 'How lucky I am to see this beautiful animal in its environment.' "

Even after the beauty and wonder that is shark, it still seems like a piece of advice that works best when you're out of the water.