And what's with all the negative vibes toward Kevin Costner? Sure, he's a little bland and egotistical, with limited range, but he also emits a quiet intelligence found in few other stars. Even in recent financial flops like A Perfect World and The War, he had an undeniably engaging presence. What I like most about Costner, though, is that he always takes slightly unusual roles. You rarely see Costner playing an out-and-out hero, he isn't afraid to wear bad hair, and he's one of the few big names in Hollywood who doesn't appear in sequels of his successful films (though JFK II is hard to imagine).

So I walked into Waterworld thinking, hey, how bad can it be? And the diagnosis: Wow. They're right. What a waste.

To be fair, Waterworld starts out well, paying grim attention to the details of life on a world without land. Only the most well-adapted sailors survive, and those who can't sail huddle together in small floating townships constructed from old ship scraps. Costner, playing a laconic character known only as the Mariner, survives by trading such rarities as dirt and dry paper. When he's on his own he makes do by eating from a tiny, rare tomato plant and peeing into a contraption that allows him to guzzle his urine. It's not just for breakfast anymore.

The mechanical details of Waterworld are impressive, with more cranks and pullies than a shopful of Advanced Lego sets. But the movie's unusual vision of the future rarely expands beyond its gadgetry. By the time the plot kicks in, the picture has lost all sense of consistency toward its story world. We're left with soggy questions, such as: Why isn't anyone fishing? If these people have jet skis, why don't they have speed boats? How do these people feel about their environment? Other than grumbling at each other, do they have a culture? And so on.

Waterworld's creators don't care to create a fully fleshed-out science fiction world; they'd rather lay out a string of action scenes full of gargantuan explosions. The movie's first such scene, in which an army of motorcycle-gang types descends on a castle-like township, is a tip-off to where much of Waterworld is stolen from: The Road Warrior. Everything's there: the punky outfits, the mythic attitude toward the hero, and even the scruffy little kid. But the crucial difference is that The Road Warrior's action sequences were raw, tense, tightly constructed events, while Waterworld's are splashy, messy and unexciting.

Feebly directed by Kevin Reynolds, Waterworld's action bits rarely seem plausible, and certainly don't moisten one's adrenal glands. Most of them are reminiscent of children's games. During the scene when jet skiers drive their boats up ramps and try to land in the circular township, I was reminded of miniature golf; a harpooned airplane uncontrollably circling the mast of a ship was reminiscent of tether ball; and the climax of the film might have been dreamt up by an executive with a yo-yo. Why is this thing rated R, anyway?

Waterworld has an extended breather section in the middle in which Costner's character unconvincingly develops from a self-centered survivor into a Mariner Who Cares. We also learn that he has gills, and may in fact be The Man from Atlantis. There is also some nonsense about a cute little girl (Tina Majorino, the only actor in the movie who appears to be having any fun) whose tattoo points the way to dry land. Talk about dumb plot points: When the bad guys catch the girl, all they need to do is copy the tattoo and let her go. Instead, they hold her down and spend hours trying to figure out the map while she squirms.

In a very lame casting choice, Dennis Hopper once again plays a cigar-chomping, cartoonish villain who kills blithely and doesn't seem intelligent enough to tread water, let alone lead a crew of baddies. Jeanne Tripplehorn, as Costner's love interest, is equally boring: She's just a pretty face with nothing to do but gawk at the hero's webbed feet.

Strangely, like Arnold Schwarzenegger's chant of "Big Mistake!" in The Last Action Hero, Waterworld contains a perfect piece of unwittingly self-referential dialogue. When everything is blowing up and the evil characters have been defeated, the little girl says coyly to the villain: "Was this your big vision?" I can't think of a more fitting question to ask the producers. It's not that Waterworld is horrible: There are good parts (although most are about as rare and unripe as one of the Mariner's tomato plants). It's just that if all the creators wanted to do was blow things up, they could have made two dozen other films on dry land that are just as entertaining. Granted, the creation of an all-water action film is pretty impressive, but you leave Waterworld feeling the disappointment of a kid who gets on an amusement-park log ride and doesn't even get wet.