There's no plot, no apparent theme, and little action. And an hour into the movie, I'm still not sure where it's going. So why is the 90-minutes as riveting as I think it is. For one, the filmmakers begin with that interesting seagull sequence that provides insight into Sandy's (Hershey) manipulative character and the boys' general submissiveness.
However, in between the opening sequence and the final one, nothing much happens. Some scenes are overlong (the pot smoking, the hair washing), while the elliptical dialog is often punctuated by long, non- meaningful, pauses.
Nonetheless, the three hedonistic kids are attractive, fairly realistic, and found horsing around at a scenic beach. But then, chubby Rhoda arrives, with her needy, yet judgmental, attitude, and it's curious where things will go from there now that an outsider is watching them.
There's an undercurrent here, especially with Sandy, that's seductive. It's to the filmmakers credit, including the cast, that they manage to mesmerize with such spare elements. Oddly, the technique reminds me of the popular Swedish auteur Ingmar Bergman— especially his Virgin Spring (1959).
I take the upshot as having to do with judgmental people who stand apart from the crowd and not being able to tolerate them. But however you take it, the movie avoids cliché (as others note) and continues to fascinate at a generally unspoken level. Too bad the Perry's didn't make more movies.