Frankie and Dolores are a young couple heading to the beach for what Frankie believes will be a quiet, romantic escape. However, Dolores, disappointed with her relationship and not wanting to be alone with Frankie, invites several friends to join them at the beach house. This causes Frankie to feel betrayed and upset, as he was expecting a private getaway. Meanwhile, nearby, an anthropologist named Professor Robert Orville Sutwell is staying in the adjacent beach house. Unbeknownst to the others, Sutwell is secretly observing the local teenagers and their behavior, especially their surfing lingo and social interactions, as part of his research on the "wild mating habits" of Southern California youth.
As the story unfolds, Frankie, encouraged by his friends, begins flirtatiously engaging with Ava, a waitress working at a nearby restaurant. His new flirtation incites jealousy in Dolores, who, in her anger, inadvertently ends up in the lap of Eric Von Zipper, the flamboyant leader of a rowdy motorcycle gang called The Rats. Despite her repeated requests to be released, Von Zipper refuses, until [Professor Sutwell] intervenes with a surprising technique that paralyzes him, allowing Dolores to escape. A developing crush blooms between Dolores and the professor, which fuels Frankie’s jealousy and prompts him to escalate his flirting with Ava. Meanwhile, Ava genuinely falls for Frankie, even though he is mainly using her to make Dolores jealous.
In an attempt to deepen his understanding of the youth culture, Sutwell tries to build a professional relationship with Dolores, but she misreads his intentions, thinking there is a romantic interest. On the other hand, Ava’s feelings for Frankie grow sincere, but his indecisiveness and mind games lead Dolores to eventually break off their relationship after she accepts his later declaration of love. At the same time, the professor’s assistant, Marianne, develops her own romantic feelings for Sutwell, who remains mostly oblivious to her hints and romantic cues.
Throughout the film, Dolores introduces Sutwell to her friends, who, while teasing him and mocking his outsider status, also help him learn how to surf. One evening, Frankie chooses to spend time alone with Ava but refuses her physical advances, adding to the tension. Meanwhile, Sutwell shaves off his beard at Dolores’s request, trying to appear younger, but remains oblivious to her romantic advances, focusing instead on his research. Von Zipper and his gang plot to sabotage Sutwell but accidentally sneak into Dolores’s room, where Dolores is alone and screams for help. Sutwell hears her distress, intervenes to disable Von Zipper again, and comforts Dolores. However, when the teenagers rush in and see Sutwell hugging Dolores, they mistakenly assume impropriety.
Later, Sutwell finally recognizes the mutual feelings he shares with Marianne and realizes Dolores’s interest in him. Just as he and Marianne share a kiss, Dolores arrives, heartbroken and angry, feeling betrayed. This sparks Frankie’s anger, leading him and his friends to confront Sutwell. They discover Sutwell’s research notes, which reveal that he has been studying the teenagers in a way that makes them uncomfortable. Sutwell then escapes to the restaurant where Ava works, but is caught by Frankie, Dolores, and the other surfers. Frankie accuses Sutwell of playing with Dolores’s heart, to which Sutwell responds that Dolores was merely using him to make Frankie jealous—the same way Frankie was using Ava.
Realizing the deception, Dolores concedes, and just as they are about to resolve their differences, Von Zipper and his motorcycle gang enter, attacking Sutwell and causing chaos. The surfers rally to protect Sutwell, and a large fight ensues. In the aftermath, Sutwell decides to leave with Marianne to continue his research in the North Pacific, and Frankie and Dolores reaffirm their love for one another, ending the story on a note of reconciliation and newfound understanding.
