Nobody bats an eye when “Ratatouille” and “Persepolis” are tallied among 2007’s finest films. And when Disney can poke fun at itself, as it does quite winningly in the live-action “Enchanted,” such heresy can only be seen as coming from a position of strength. Film animation, it seems, has reached a new golden age.

And so it bears remembering that kids (to say nothing of their parents) had to be dragged to big-screen cartoons just 20 years ago, well before the days of ogres and Incredibles and Belleville triplets and tap-happy penguins. “The Little Mermaid” changed that in 1989. A pair of shrewd and slightly bratty off-Broadway songwriters named Howard Ashman and Alan Menken (“Little Shop of Horrors”), while following the typical Disney playbook of defanging their source material, gave the seemingly moribund genre a brisk and unabashedly emotional transfusion with this film and, two years later, with “Beauty and the Beast.”

As critics gushed at the time, most Broadway musicals would kill to be half as clever and touching and tuneful as these films. So Disney has turned “Mermaid” into the latest of its high-gloss screen-to-stage projects — and the result is almost exactly half as clever and touching and tuneful as the film. This represents progress of a sort for the entertainment juggernaut, which sent audience expectations sky-high in 1997 with its visually rapturous stage adaptation of “The Lion King” and has dashed them with each subsequent production. Like that notable success, which catapulted Julie Taymor into the upper echelon of stage directors, “Mermaid” draws upon the expressionistic talents of another opera denizen, Francesca Zambello.

Ms. Zambello’s embellishments, for the most part, are not particularly welcome ones. While the new songs (Glenn Slater has augmented the original lyrics by Ashman, who died in 1991) sit alongside the old ones comfortably enough, none of them pose a threat to the original Big Three — “Part of Your World,” the Oscar-winning “Under the Sea,” and the irresistible “Kiss the Girl” — in terms of lodging themselves into audiences’ heads. Doug Wright has added backstory galore and a handful of grin-worthy puns (“As long as you live under my reef, you’ll obey my rules!”) but allows the action to bog down well before the final chorus. And while directors Ron Clements and John Musker created a film aesthetic that combined picture-book spectacle with a newfound attention to the characters’ emotions, Ms. Zambello’s physical production is most notable for Natasha Katz’s retina-searing lighting, and a huge turquoise-and-gold orb by set designer George Tsypin that might have rolled in from an Albuquerque roadside stand.

All the same, the narrative heart that Ashman and Mr. Menken helped revive with such precision and care has survived the intervening two decades more or less intact. Hans Christian Andersen’s fairy tale may have lost its grislier details, as well as its somber ending, on its way to Hollywood, but the tale of the headstrong Ariel (Sierra Boggess) risking life and fin to vie for the love of Prince Eric (Sean Palmer), with various anthropomorphized helpmates in tow, remains a diverting and even affecting fish story. Until an unnecessarily soggy ending, Ms. Zambello and Mr. Wright give the action a kinetic force that fleshes out several of the smaller characters without drawing undue attention from the central love story.

Much of this energy springs from the show’s near-constant movement. “Mary Poppins” excepted, Disney’s musicals have hardly been known for their dancing. That show’s co-choreographer, Stephen Mear, takes the reins here, and the results are largely successful. A gaggle of gulls navigates a funky tap routine while wearing giant clown shoes, and Ariel’s six sisters cut loose with infectious bravado in the girl-group stomp “She’s in Love.” But Mr. Tsypin’s frequent use of Mylar strips along the bottom of the stage, designed to draw attention away from the actors’ legs and toward their undulating tails, necessitates an awful lot of jumping as the performers make their way up and down the stage. And Ms. Zambello’s much-discussed use of those wheeled Heely shoes, while permitting the cast to simulate underwater movement with gliding ease, constrains all but the nimblest performers during several protracted dance sequences.

Two of these sequences are the film’s centerpiece songs, both led by Ariel’s hapless minder, the Caribbean crab Sebastian (Titus Burgess). Mr. Burgess takes Sebastian’s original keys up at least an octave, turning the seduction ballad “Kiss the Girl” into a Smokey Robinson-style quiet storm. As comfortable as he is in these numbers, however, Mr. Burgess forces too many of the sight gags and often finds himself engulfed by his surroundings. This disparity between vocal prowess and overall presence haunts several other lead performers. As the dashing Prince Eric, Mr. Palmer has a very nice pop tenor and, well, a very nice pop tenor.

And while Ms. Boggess’s formidable belt voice could shatter a glass-bottom boat, even while bent at the waist to mime swimming, she struggles to conjure much beyond a by-the-numbers adolescent impulsiveness. Perhaps sensing the dangers of literally muffling what is by far their star’s strongest quality, the creators have fudged the issue of Ariel’s muteness as a condition of her receiving legs. This Ariel gets to “think out loud,” voicing her concerns in a handful of Act 2 songs that are not among the show’s finer entries.

The supporting cast includes the cream of off-Broadway talent (Heidi Blickenstaff of “[title of show],” Tyler Maynard of “Altar Boyz”), who are generally saddled with the flimsier roles, and a slew of veterans who make do with slightly better material. Norm Lewis’s chiseled King Triton is Broadway’s most impressive merman since Ethel, and Eddie Korbich’s vaudevillian brio almost but not quite papers over a litany of dreary malapropisms as the well-meaning seagull Scuttle. The primary beneficiary of Mr. Wright’s augmentations is Sherie René Scott as the voluptuous villainess Ursula. Sashaying her voluminously padded hips like a maritime Mae West (although it’s a lot easier to be leggy when you’re an octopus), Ms. Scott turns her sultry manifesto “I Want the Good Times Back” into the evening’s closest rival to matching the heights of the original material.

As often happens when something stays underwater for too long, the stage “Mermaid” begins to bloat by the end. Mr. Wright’s finale incorporates scraps of Milton (a fallen deity battles to regain supremacy), Cinderella (Eric seeks his princess by testing vocal cords instead of feet), and even other Disney shows (a French chef’s trifle of a song has been expanded into an extraneous “Be Our Guest” knockoff), each to marginal effect. Preventing the luscious Ms. Scott from adopting the va-va-voom persona of Ariel’s romantic nemesis, as in the movie, is an odd choice. So is having characters thank one another for heroic acts that no longer exist in the script.

After the excruciating “Tarzan,” Disney had nowhere to go but up in terms of staging its animated film properties. And if “The Little Mermaid” is at its most successful when it merely apes the original film, the Ashman/Menken material holds its own against the vast majority of scores that have reached Broadway since 1989. Becoming part of Broadway’s world was inevitable for young Ariel, given the success of “The Lion King.” After 18 years, though, our plucky heroine still has yet to find her sea legs.

Open run (205 W. 46th St., between Broadway and Eighth Avenue, 212-307-4747).