While watching an entirely unsuccessful production, there exists a natural human urge to jump up and fix it. Some pieces are wrongheaded from the get-go; some texts are unsalvageable. But often a show will show a ghostlike glimmer of promise, which someone should have been able to tease out. That’s when the irritated theatergoer dreams of yelling out “Pick up the pace, kids!” or pleading with the crew not to do that interminable set change … again.

The specter of quality is faint indeed in Amy Merrill’s “Driving on the Left Side,” a cliche-ridden horror about finding love on vacation in Jamaica. Yet had the production team moved into the breach, they could have helped gloss over the script’s worst inadequacies. For large sections, a halfway decent reggae band plays onstage, and, handled differently, jamming with “Reggaelution” could have dulled our pain. One actor (alone among four) actually manages to squeeze a few drops of lifeblood out of Ms. Merrill’s stone – so clearly potential does exist. But, ignoring their few assets, the show instead stands as a step-by-step manual on how to ruin an audience’s evening.

Primary guilt lies with the playwright – especially since Ms. Merrill founded the production company that has mounted her show. Both endless and aimless, the play follows tourist Serena (Jennifer McCabe) who latches onto a taxi driver (Postell Pringle) who is trying to follow his dream. Cowboy, who sings reggae when he’s not in the cab, isn’t averse to a little flirtation with the jilted bride from Buffalo. But his flirtation is her momentous romance, and poor Cowboy finds her hard to shake.

This, at least, is the play we see. Read Ms. Merrill’s script, however, and it’s clear that she sides with the romance dazed tourist. “The audience roars in approval,” she writes in a stage direction when Cowboy and Serena dance together, or she has him stumble whenever Serena enters in “a becoming dress.” Unfortunately, she fails to write a single dialogue between the two that hints at even a nascent attraction. Their conversations are all selfish and one-sided: Serena is demanding and rude and her hero barely has time for her.

Stories about finding love in Jamaica have been ending badly these days. Most famously, Terry McMillan’s island romance that inspired “How Stella Got Her Groove Back” is now dying a nasty death in divorce court. Let that be a caution to our heroine. As in “Stella,” a buttoned-up woman from the States learns about love and letting go by hooking up with a local. But the “real Jamaica,” an oft-repeated phrase, does not exist simply to liberate lusty foreigners. Ms. Merrill clearly feels strongly that Jamaica has its own problems, and tourists who fall in love with its “innocence” are guilty of the worst condescension.

Again, a kernel of possibility exists here, and if Ms. Merrill had the pen for it, the story of the “real Jamaica” would have been a good one. When Sharon Tsahai King enters as Cowboy’s mother, we hear echoes of that unwritten, better play. She plays very broadly, but her good humor and ease with her own failings trump some of her clunkier lines. Locked into a romance with the nearly unwatchable Paul Navarra (as Serena’s drunkard father), it’s quite painful to see her bonhomie simply going to waste.

Director Florante Galvez makes common, but disastrous, mistakes. Though Mr. Pringle has the easy gait of Cowboy down pat, Mr. Galvez can’t get him to look at his co-star without wincing. Ms. McCabe, on the other hand, looks on the verge of beating the entire company to a pulp. Her grim, angry attitude never changes – you can feel her vibrating with rage even in the “romantic” moments. Mr. Galvez also lets Mr. Navarra get away with some awful mugging – at one point he actually bites his finger when he catches a glimpse of Ms. King’s behind.

Then Mr. Galvez adds a half-hour to the running time with lackadaisical, unnecessary set changes. With a band in the show, he still pipes in pre-recorded reggae for these overlong intervals. Sure, the script he was handed was a dud. But by bringing “Driving” to a screeching halt time and time again, he douses the few sparks that might have flickered into flame.

For a how-to of a slightly different nature – a primer in charm, for instance – head uptown to the McGinn/Cazale Theater to catch Adam Bock’s “Swimming in the Shallows.” In this frolic about love, three couples meet, marry, or separate. They aren’t the usual couples we see on stage – lesbians, the middle-aged, and interspecies affairs can all legitimately complain of under-representation.

An allergy to cliche keeps the piece fresh (not another boy-meets-shark romance, I can hear you groaning), and spotless, idiosyncratic performances keep it buoyant. “Shallows” is right – the show speeds by, with everything from gay marriage to Buddhism as a laughing matter. But under Trip Cullman’s clever direction, we find the shallows just as fraught as the big, dark sea.

Until July 31 (312 W. 36th Street, between Eighth and Ninth Avenues, 212-868-4444).