The title Mean Creek is a kind of plainspoken, water-borne homage to ''River's Edge,'' a beloved and influential 1986 movie about adolescent moral choices. But really, first-time writer-director Jacob Estes' terrifically harrowing tale of a bully, a victim, and a plan for revenge is as much an economical teenage version of ''Heart of Darkness'': The young people paddling downstream on a soft summer day in this unusually perceptive and fluid American indie have little idea what personal crises they're in for, or on what shore their shared trauma will deposit them.
Indeed, all they have in mind when they begin is some excellent revenge on a kid who clearly deserves it. George (Josh Peck from Nickelodeon's ''The Amanda Show'') is fat, nasty, and provocatively obnoxious, with a swaggering aggression that can turn ugly at the trip of a verbal trigger. After being the victim of George's violence one too many times, the smaller, shyer 13-year-old Sam (Rory Culkin, who shows a sophisticated taste by choosing projects like ''Igby Goes Down'' and ''You Can Count on Me'') confesses his torment to his older brother Rocky (Trevor Morgan from ''The Patriot''). And Rocky dreams up a suitable retaliation involving mild harassment and major humiliation: They'll invite George on a birthday party riverboating trip and then, at the appropriate time downstream, pants the creep and leave him wet and naked.
In classic band-of-brothers form, Estes establishes the contours of the avenging party in concise strokes. Rocky enlists another older teen rebel, Marty (Scott Mechlowicz), whose own internal demons make him all too joylessly happy to participate. Clyde (''Smallville'''s Ryan Kelley) joins up as a respite from fending off taunting accusations of homosexuality. Millie (Carly Schroeder from ''Lizzie McGuire'') is included among the boys because she's Sam's budding girlfriend.
But as Estes builds toward inevitable crisis and surprising consequence, suspending the tension with handsomely impressionistic handheld cinematography (much of it shot with available light by Sharone Meir on the water near the Oregon/Washington border), the filmmaker simultaneously unleashes his most unnerving psychological weapon: George is a bully, but he's also a lonely, sensitive kid who keeps a poetic video diary. This tormenting provocateur, capable of such unrelenting cruelty, is also brought up well enough to recognize the dangers of not wearing seat belts or life jackets; because he believes he has been invited to a birthday party, he politely brings a gift. It's rare to see an actor of any age, let alone a teen like the usually comedic Peck, carry off the challenge of portraying ugliness and vulnerability with such aplomb.
And although the talent of a kid with the last name of Culkin may not, at this point, register as such a novelty -- Rory follows brothers Macaulay and Kieran -- there is something precociously mature but natural about the work of this youngest Culkin sibling that stands apart. His Sam is a marvel of believable hopes and anxieties, a boy who doesn't quite know how to kiss a girl or what the right thing is to do during a meltdown of group dynamics. But his instincts, like those of this impressive, modern morality tale, are sound.