In the program notes to his new drama, “Trial by Water,” the playwright Qui Nguyen recounts a story from his boyhood. In 1988, he arrived at the Little Rock airport with his family to pick up his 10-year-old cousin, a refugee from Vietnam, and found himself in a crush of clamoring photographers.

The cousin, Hung Tran, was but one of the thousands of so-called “boat people” who fled Vietnam rickety fishing boats, but this boy had made the crossing under particularly gruesome conditions. Of the 110 desperate, starving passengers stranded aboard the broken-down Bolinao in the South China Sea, only 52, including Hung, survived. A few months later, Hung would tell his cousin he thought his soul was dead.

This true story serves as both jumping-off point and inspiration for Mr. Nguyen’s fictionalized tale of two brothers’ experience aboard a small refugee ship bound for the Philippines. The story unfolds on the lower deck of the ship, represented here by an extraordinarily deep woodenplanked set that stretches far into the recesses of the theater.The thin cast of characters is filled out through the use of large puppets, who wear the same conical rice-paddy hats as their human counterparts, blending into the crowd.

Given the eerie set and the grim situation of two teenage brothers traveling alone, in fear of the elements and their fellow passengers, the play’s first lines are startling. Huy Tran (Genevieve DeVeyra), a horny 13-year-old, is complaining to his big brother Hung (Dinh Doan) about leaving behind the prostitutes in the neighborhood, to whom he planned to lose his virginity. Hung reassures his kid brother by giving him a wallet-size picture of an American pinup girl and letting him run on about his fantasies. The dialogue might as well be from a teenage boy flick like “American Pie.”

Right from the start, Mr. Nguyen wants to strip his characters of affected romanticism. Just because they are refugees, the playwright says, doesn’t mean they don’t tell crude jokes and fight constantly about stupid issues. But in attempting to make its characters “normal,” the play runs into two problems. First, there’s the annoyance of having to listen to the petty, agitated bickering of two teenage brothers. Second, the play has trouble finding its tone – jokes about American girls insisting on anal sex don’t coexist easily with banter about drinking your own urine to stay alive.

This is a problem throughout “Trial by Water.” The critical character of Tien (Arthur Acuna), a former acquaintance of the boys’ father who tries to befriend them, is meant to be a menacing, volatile figure. Yet he makes the feeblest puns imaginable – over and over again. When the passengers’ cold-blooded Darwinism descends into cannibalism, Hung tells Tien, “We just want to make it to America in peace.” Tien responds, “How about in pieces?”

How are we supposed to respond to these jarring, seemingly tasteless, decidedly not-funny jokes? Director John Gould Rubin never seems to find a satisfactory answer to the question. Throughout the play, these bad bits of dialogue drop like lead bricks.

Matters are not helped by Mr. Nguyen’s scene structure. After a while, the play starts to seem like a series of acting-class exercises where the students are advised against giving their scene partner what he or she wants.This is taken to absurd levels in “Trial by Water,” with the hapless Hung spending most of his time shouting at other people. Meanwhile, his little brother’s habit of constantly arguing and contradicting makes him come off as a hateful, bratty child.

Despite all this, Mr. Doan gives some dimension to Hung, the conflicted Buddhist who isn’t sure when to abandon philosophy for pragmatic survival, and Ms. DeVeyra is able to make you instantly forget that a woman is playing a young boy. But only Karen Tsen Lee, who plays the boys’ tortured mother in a series of flashbacks, makes you believe she is truly living in Vietnam in the 1980s, wracked by choices between family and ideology, safety and freedom.

Mr. Nguyen’s play too often feels like an essay put together to prove a series of points: Politics destroy people, religion alone is not enough, anyone can lose his humanity under the right circumstances. To demonstrate the latter point, the play’s final twist turns Hung into not merely a reluctant participant in horror, but an enthusiastic sadist. Given what has come before, this simply isn’t credible.

There are echoes, in the deep chamber of this leaky ship, of what many actual boat people must have endured. It seems that story could only be told as a tragedy. By oscillating between comedy and melodrama, “Trial by Water” squanders the power of its powerful story.

Until April 9 (45 Bleecker Street at Lafayette Street, 212-253-7017).