�Mermaids� (PG-13)

An enduring mystery of the movies is that some of the most troubled productions bear the sweetest fruit. "Mermaids," the new mother-and-daughter comedy with Cher and Winona Ryder, is an extreme case in point -- a film that seemed destined for ashes that rises up, instead, in goosey triumph.

Few films have had such a tortured birth. During the course of production, the film had three directors, beginning with Lasse Hallstrom, then Frank Oz, and finally, Richard Benjamin. Hallstrom left six weeks before shooting began because of creative differences, taking Emily Lloyd, who was slated to play the daughter, with him. Enter Frank Oz and Winona Ryder. Then two weeks into shooting, exit Frank Oz, again because of creative differences. Then Benjamin took over. A prescription for disaster if ever there was one.

Miraculously, though, "Mermaids" has held fast to its spirit of wiggy nonconformity. The strength of June Roberts's sprightly, inventive script -- which came by way of Patty Dann's novel, with some custom modifications based on Cher's relationship with her own mother -- may have been the project's salvation. Set in 1963, the film is about a family of three women. The film emerges from the point of view of Charlotte (Ryder), an overwrought 15-year-old with a fierce yearning for conformity, for normality and a stable, all-American life. Her dream of dreams is to become a nun -- certainly a laudable goal for a young lady. And to this end she sleeps with a crucifix, prays to the saints, even fantasizes about self-flagellation. Problem is, she's Jewish.

The other problem falls under the heading of carnal urges. As much as she would like to remain pure and celebate, she falls in love at the drop of a hat, most recently with Joe (Michael Schoeffling), the handsome young caretaker at the convent near their new home on the Massachusetts coast.

In this she is very much her mother's daughter. Mom -- or, as the daughter calls her, Mrs. Flax -- is the original wild child, uninhibited, impulsive, pathologically unconventional. Dressed in her modish bell bottoms, butt-hugging minis and "That Girl" bouffant, she's a cruise-mobile, keeping the eagle eye out for passengers who might be going her way. If she wants to sleep with someone, she sleeps with him. (That's how she came by her two daughters.) Her habits are disruptive to the family, though, because when the lovers get too close she bolts, packing up the family and all their earthly possessions and starting over.

The film's comedy springs out of the incongruous pairing of a rebellious, crazy mom and a devoutly conservative daughter -- that and the nuttiness of having a Jewish girl obsessed with Catholicism. The ground the movie covers is not unfamiliar; it's a young girl's coming-of-age story. But Roberts's script invigorates the material with a quality of everyday surrealism. These are deeply eccentric characters, and more than a little nuts. Charlotte clunks around like a gimpy swan in ugly rain boots because "they're from him," says her sister, Kate (Christina Ricci) -- "him" meaning her father, whom she dreams about as a kind of loving deity in two-toned shoes. Kate is a swimming fanatic, and for a time she floats on the edges of the action, saying practically nothing, as if she were the family dog.

Kate may in fact be part fish, but all the women characters here are seen as exotics -- charmed creatures from a world all their own. For some this notion might be hard to swallow. But Cher, who's the most ravishingly otherworldly of modern actresses, makes the suggestion seem altogether reasonable. Her Mrs. Flax is deliciously trashy -- kitsch in high heels. She hates anything ordinary; even when she makes sandwiches, she cuts them into star shapes.

Of course, she's an embarrassment to Charlotte, who feels most of the time as if she's the mom. She wants a more normal mother, and so when Mrs. Flax becomes involved with Lou (Bob Hoskins), a shoe-store owner from the village, she immediately begins building "Father Knows Best" fantasies in her head.

What's great about "Mermaids" is how easily it keys us into Charlotte's hilariously warped teenage thought-waves. Ryder gets most of the credit for this. Having made something of a specialty of woe-is-me, adolescent angst, Ryder finds a deeper level here, a level of comedy with something genuinely painful mixed in. There's a precocious, child-woman quality to Ryder; she has the smarts of an adult and the rawness of a kid, and that's perfect for Charlotte. Plus she makes the fantastical side of Charlotte's inner life -- for example, her belief that after kissing Joe in the bell tower of the convent, she is pregnant with the first Jewish-Italian messiah -- entirely plausible. It's her richest performance.

The movie is gloriously designed (by Stuart Wurtzel) with aquarium-bright colors that slip with the buoyant period music into your bloodstream. There are flaws -- the sequence built around the assassination of President Kennedy feels perfunctory; it doesn't fit really, and you feel as if it's been added for cheap sentiment. Plus you feel at times that the movie is laying on the endearing eccentricity of its characters a little thick. For the most part, though, the movie lets us come to it, lets us have our own reactions, without bullying us with maudlin emotion; it stays away from that "Beaches" feeling.

Richard Benjamin's direction isn't inspired; he might have given the narrative a little more snap. And the conflicts don't have the emotional resonance they might if some of the darker shades in the story had been allowed to develop. Still, it's his best work since "My Favorite Year"; maybe his best work ever. But what's lost in momentum is gained back in the unexpectedness of the jokes and the quality of the performances. There are subtle touches throughout, like the way Kate suddenly begins talking without anyone commenting on it. Or the sweet way Lou establishes his relationship with the girls. (Hoskins is irresistible; he is a pro, as always, but at a very high level.) "Mermaids" is an infectious, bouncy diversion, like the fruity dance the girls and their mother do around the kitchen table at the film's end. It gets you humming along.