That one of Robert J. Siegal’s early films — “Parades,” the first theatrical American film to challenge the U.S.’ role in the Vietnam War — premiered at a USA Film Festival nearly 30 years ago, testifies to this veteran filmmaker’s staying power. With his latest outing “Swimming,” he proves that you don’t have to be a just out of film school Gen-X’er to make a resonant and entertaining movie about young adults. As another summer arrives in Myrtle Beach, SC, Frankie Wheeler (Lauren Ambrose) grows increasingly disenchanted. Slaving away in the family burger joint by day and cruising the boardwalk with her sassy and sexy best friend Nicola (Jennifer Dundas Lowe) at night, the cute and practical tomboy is well aware that she’s merely treading water. It takes two newcomers to shake things up for her. First it’s Josee (Joelle Carter). Hired as a waitress by Frankie’s brother, Josee is a quintessential blond beach bunny…except that she seems to be attracted to Frankie as much as if not more so than to the plethora of muscle-bound hunks who shamelessly gawk as she sashays by. As if Josee doesn’t have the suddenly confused Frankie’s hormones in enough of a dither, in wanders Brad (James Villemaire), a hemp-friendly drifter who makes a living selling tie-dye T-shirts out of the van he shares with his dogs. Used to being the center of attention, an increasingly jealous Nicola chafes at the attention the newcomers are suddenly showering on her unassuming satellite. As the summer heats up, so do the competition and the passion, romantic and otherwise. This finally forces the two lifelong friends to come to terms with some unsettling new realities on the boardwalk. Okay, first of all, for those of you pathetic droolers still hung up on that bit about Josee being attracted to Frankie, go rent “The Erotic Witch Project” and get the lasciviousness out of your system before you settle in for “Swimming.” Yes, there is a very palpable lesbian erotic undercurrent pervading this film. However, the reason it’s so palpable is because it’s so subtly and deftly handled…AND it’s only one thread of the film’s storyline. Possibly mellowing, Siegal doesn’t break much new ground with “Swimming,” unlike the controversial and vehemently anti-war “Parades.” Instead, he does a wonderful job capturing the festive but tacky atmosphere of his beach town world and pulls solid performances out of his cast of not-quite-familiar faces in a charming film that’s as much about family, friendship and coming of age as it is about summer love and romance.