Toward the end of the first act of "My One and Only," Tommy Tune and Sandy Duncan find themselves marooned in a tropical landscape that, in the chic, minimalist view of set designers Adrianne Lobel and Tony Walton, happens to be an upended yellow square, a single green Art Deco palm frond, a panel of blue sky and an oblong pool.

Giving in to the love that has been percolating between them for an hour or so, the two stars slither off their table-top beach, ankle into the water and before long are kicking up a summer shower to the strains of " 'S Wonderful."

They are an utterly improbable couple. He stands 6-foot-6 and has the long limbs of a grasshopper. Under the Texas farmboy's modesty, he still seems to be mildly surprised at what puberty did to him. She barely comes up to his shoulders, but has spunk on her side and a smile that can go from little-girl-lost to little-girl-devilish in a trice. If he is loose and lanky, she is piston-driven.

But as they dance together in the H2O, a hint of friendly malice qualifying their merriment, they do seem like the perfect playmates for a rain puddle. The ebullient number pretty much encapsulates the show as a whole. It is bright, splashy, stylish and utterly determined to drench everyone in a good time.

"My One and Only," which has taken up a six-week residency in the Kennedy Center Opera House, is also as shallow as that wading pool. But I suspect that no more than one in a hundred is likely to object. This is the essence of Broadway musical comedy as it used to be practiced back in the days when shows were occasions for singing and dancing, the chorus was energetic and attractive, the stars got to perform like stars, and High Art was just a drunken drummer in the pit. A plot was then deemed perfectly worthy if by the final moments the boy got the girl he'd met and then misplaced earlier in the evening.

Ironically, "My One and Only" had other ambitions when it began its tumultuous tryout a couple of years ago. The original idea was to take a dozen or so standards by George and Ira Gershwin and create a new musical around them that would reveal the songs in an ironic and biting light. Peter Sellars, the director of the Kennedy Center's soon-to-debut American National Theater, was at the helm. Timothy Mayer was writing the book. And the show, apparently, was taking on the fairly acidulous tone of the 1981 movie "Pennies from Heaven" when the plug was pulled in Boston.

Peter Stone was called in to overhaul the story; and Tune and Thommie Walsh took over the staging. By the time it reached New York, "My One and Only" had become the high-gloss entertainment it is now. If it no longer has a thought in its head, it's certainly got an attractive head and some spiffy 1920s beaded hats, too. The book may be positively jerry-built, but the songs remain the top of the line. Any show that gives you "Soon," "High Hat," "He Loves and She Loves," "Boy Wanted," "Blah, Blah, Blah," " 'S Wonderful" and "Strike Up the Band" in the first act alone is not stinting on the riches. Since, in addition, most of those songs inspire some of the slickest tap-dancing this side of "42nd Street," it seems ungrateful to speculate on what the show might have been.

Tune is cast as Captain Billy Buck Chandler, an intrepid barnstorming aviator who wants to be the first man to cross the Atlantic nonstop so he can get his picture on the cover of Time and duly impress English Aquacade star Edith Herbert (Duncan). Billy Buck, as his pint-sized lady mechanic (Peggy O'Connell) reassures him, is "not a hick -- a hayseed, maybe." But face it: Edith is a world famous personality -- "the third woman to swim the English Channel, the first attractive one." She also has a past, along with some compromising photographs to prove it, and her dastardly Russian impressario (Don Amendolia) is not about to let her out of her gilded swimming pool.

To hone his courtship techniques, Billy repairs to a certain Mr. Magix, the venerable Charles (Honi) Coles, who could probably teach a grizzly bear to be graceful. The usual approach to tap dancing has never been Cole's. While others tend to pick up the speed progressively, multiply the staccato taps and build to a climax of machine-gun fire, Cole goes the other way -- starting out easy, graduating to casual and ending up effortless. In the evening's biggest crowd-pleaser, he lays out the steps to "My One and Only" and Tune dutifully follows suit. The two pros make it look as simple as falling off a log.

Actually, just about everywhere the show wanders -- to the uptown church-by-day, speakeasy-by-night of the Rt. Rev. J.D. Montgomery (Tiger Haynes); to Central Park under a full moon; to that sun-drenched tropical sanctuary, which turns out to be an island called Staten; to Morocco, for heaven's sake -- it quickly finds a reason to get everyone dancing. The courtship of Billy and Edith may not exactly lift your spirits, but all the flying feet and flapping elbows surely will.

In fact, Tune and Duncan don't register so much as lovers in the making as they do potential best friends. The romance in "My One and Only" has always been fairly androgynous. Twiggy, the original Edith Herbert, seemed to bring out the protective instincts in Tune, and when they danced together -- she, with charming gaucherie -- it was as if a big brother were watching out for his favorite sister.

Duncan is far surer of her skills, which changes the equation. She gives a snappy, upbeat performance -- and virtually belts her numbers to the back row. This Edith, you find yourself thinking, could probably fend for herself. But there's a price to pay for that: where Tune was once able to take charge with his aw-shucks affability, it doesn't seem quite enough now. Heartbroken over losing Edith at the end of the first act, he sings "Strike Up the Band" as if it were a torch song. But, as he interprets it, this is heartbreak on a small scale -- rather like finding your high school sweetheart has been assigned to a different homeroom.

Still, if Billy and Edith never go much beyond cute (sexy is out of the question), the show is a triumph of style. The sets are high tech sleek, the costumes Fred Astaire dapper. With the New Rhythm Boys, a trio of smart dancers in black tuxes and white spats, "My One and Only" even has a jivey Greek chorus of sorts. When "Strike Up the Band" crops up a second time -- as the show's red, white and blue finale -- it unabashedly revels in the broad stripes and bright stars, and then for good measure throws in some cartwheels and a spangled baton-twirler.

They aren't supposed to be writing shows like this any more. But they did. And it works. Let Stephen Sondheim engineer the breakthroughs. "My One and Only" is content to take a bold step backward into the cloudless adolescence of musical comedy. My One and Only. Music and lyrics by George and Ira Gershwin. Book by Timothy Mayer and Peter Stone. Staged and choreographed by Tommy Tune and Thommie Walsh; scenery, Adrianne Lobel and Tony Walton; costumes, Rita Ryack; lighting, Marc B. Weiss. With Sandy Duncan, Tommy Tune, Charles (Honi) Coles, Don Amendolia, Peggy O'Connell, Mark East, Walter Hook, Adam Petroski, Casper Roos and the New Rhythm Boys. At the Kennedy Center Opera House through April 14.