THEATER REVIEWS : Romance Goes With Comedic Floe in SCR’s ‘Green Icebergs’ : Captivating work by Newport Beach’s Cecilia Fannon revolves around the foibles of two O.C. couples.

COSTA MESA — When underwater plankton become abundant on the lower depths of an iceberg, the iceberg can become so lopsided that, on rare occasion, it tips over, revealing the previously unseen greenery of the plankton.

Or so we’re told in “Green Icebergs” at South Coast Repertory. Just as the iceberg finally reveals its true colors, so do the people in Cecilia Fannon’s captivating romantic comedy.

But not all of her characters are equally “green.” While the upheaval in these people’s lives resuscitates two of them, two others turn their lives over and over, without much of anything to show for it.

The action of Fannon’s play occurs far from actual icebergs, in a seductive Tuscan town where two Orange County couples in their mid-30s, each married for nine years, are vacationing. The human icebergs begin to upend when Justus (Jeff Allin) mistakes Veronica (Nike Doukas) for his own wife, Beth (Annie LaRussa), while approaching her from the rear in a cafe as he reads a book.

The misidentification is quickly cleared up. But ambivalent feelings about their marriages soon surface in the conversation between Justus and Veronica, kindled by the story in the book Justus is reading. It’s about Fra Filippo Lippi, the Renaissance priest and painter who defied convention by seducing and marrying a nun. Soon the two Americans are defying convention themselves.

The new coupling becomes painfully obvious when the four tourists--including Beth’s husband, Claude (Robert Curtis-Brown)--share a dinner table that night. It becomes even plainer the following morning. Drastic measures are taken.

After intermission, more than a year has passed, and the four reunite at the same hotel and restaurant, but under very different circumstances. Only at this point is it revealed how truly green each character is.

Though Fannon plays her most predictable narrative card in the first act, she has saved enough surprises for the second to keep interest high. Among them, Fannon successfully rebuts Beth’s earlier complaint that Justus and Veronica seem to be in a movie while Claude and Beth are in the audience.

In fact, Fannon pulls off the difficult task of keeping her entire quartet alive and involving while nevertheless making it clear whose side she’s on. She makes a moral statement, about the superior value of long-term compatibility over short-term passion, yet she never sounds moralistic or preachy about it.

Her viewpoint isn’t necessarily restricted to marital matters either. She also displays a fine-tuned sensitivity to the general importance of keeping private affairs private, of considering other people’s feelings even when they’re no longer part of your life. When some of her characters attempt to cash in on their personal stories, we get a whiff of the similar concern felt in Alan Ayckbourn’s masterful “Man of the Moment,” at this same theater a year ago.

This play isn’t as funny as Ayckbourn’s, but it does have more than its share of witty one-liners, especially for a Southern California audience that knows, for example, what Souplantation is like. Only a few of the jokes stretch too far for a laugh, most notably one near the top of the script, when we hear an absurd story of why Claude stopped playing tennis, which we’re apparently supposed to believe.

Fannon demonstrates a good ear for writing different kinds of engaging talk for her different kinds of characters. Justus, for example, knows how to use big words, while Claude knows how to use brusque ones.

Fannon takes her biggest risk with an omniscient moderator--a waiter (Hal Landon Jr.) who anticipates every order, has a handy homily for every occasion, even counsels one of the characters in a scene away from the cafe. He’s an abstracted memory more than a real person, and he could become insufferable, except that Fannon recognizes this and deftly takes advantage of it in her second act.

This play won South Coast’s final California Playwrights Competition (Fannon is from Newport Beach). Unlike some of the previous winners of that contest, it has been given a Mainstage production--and, as one expects from SCR, a classy one.

Director David Emmes directs a pitch-perfect cast. Doukas’ throaty allure and Allin’s loping charm heat up the first act, while LaRussa and Curtis-Brown carefully transform their characters’ worst qualities into strengths in the second. Lighting designer Tom Ruzika got to play with romantic Italian light on Robert Brill’s sun-washed set, while Ann Bruice’s costumes help delineate the transformations of Beth and Justus, in particular.

For the record, this is the second SCR play in a row (A.R. Gurney’s “Later Life” just closed Sunday) about Americans who are (or were) inspired to tryst while in Italy. The Italian restaurants around South Coast Plaza should be doing a booming business.

* “Green Icebergs,” South Coast Repertory, 655 Town Center Drive, Costa Mesa. Tuesdays-Saturdays, 8 p.m.; Sundays, 7:30 p.m.; Saturdays-Sundays, 2:30 p.m. Ends Nov. 20. $26-$36. (714) 957-4033). Running time: 2 hours, 20 minutes.

Hal Landon Jr.: Waiter

Nike Doukas: Veronica

Robert Curtis-Brown: Claude

Annie LaRussa: Beth

Jeff Allin: Justus

By Cecilia Fannon. Directed by David Emmes. Sets by Robert Brill. Costumes by Ann Bruice. Lighting by Tom Ruzika. Music and sound by Michael Roth. Stage manager Julie Haber.