Francie Lawrence, a tomboy nearing her seventeenth birthday, is chided by her girl friends for her lack of interest in the opposite sex. To insure that Francie does not become a “social outcast,” her friends take her to the beach on a “manhunt.” When Francie decides she would rather go swimming than flirt with the surfers, however, her friends leave in disgust. While paddling out to sea, Francie becomes caught in a bed of kelp, prompting Moondoggie, one of the surfers, to free her and give her a ride back to shore on his surfboard. Thrilled by the sensation of riding a wave, she decides to become a surfer, even though the boys deride the diminutive Francie as a “gidget,” a girl midget. At home, Francie begs her doting father Russell for $21.50 to buy a used surfboard, and Russell gives her the money as an early birthday present. Francie hurries back to the beach to buy her board and there meets Kahoona, an unemployed surf bum idolized by all the younger surfers. When Francie questions Kahoona’s lack of ambition, he explains that after flying fighter planes during the Korean War, he became disenchanted by the rules and regulations of society and opted for the life of a surf bum. Later, Moondoggie tells Kahoona that he wants to follow him in his search for the endless wave rather than return to college, the path favored by his father, a successful businessman. That night, Francie asks her mother if there is something wrong with her because she is not interested in dating, prompting her mother to assure Francie that “one day the magic will strike.” At the beach the next day, Kahoona dubs Francie their mascot. For her initiation right, the surfers order her to dive repeatedly into the kelp bed. When she becomes twisted in the kelp and fails to surface, Moondoggie rescues her once again. Woozy from the incident, Francie is confined to bed and diagnosed with tonsillitis. In a fever-induced dream, she sees Moondoggie, and upon awakening, tells her mother that she “has found the one.” Although told that she must stay in bed for two weeks, Francie uses the time to refine her surfing techniques by jumping up and down on the mattress. One month after returning to the beach, Francie becomes a full-fledged surfer when she rides a wave in with the rest of the gang. Moondoggie hugs her in congratulations, but when his girl friend appears, he loses all interest in Francie. Upon learning that a luau will be held at the beach to cap the end of summer, Francie longs to attend, even though the others think that she is too young for the wild party. To attract Moondoggie’s attention, Francie offers to pay Hot Shot, one of the surfers, to take her to the luau, explaining that she wants to make someone jealous. Hot Shot agrees on the condition that he not be required to pick her up and that Francie wins Kahoona’s permission to attend. When Francie bribes Kahoona by promising to bring him some steaks, he jovially accepts her offer, but his mood quickly changes after he enters his hut and finds that his beloved pet bird has died. Sensing Kahoona’s loneliness, Francie asks if he longs to return to the time before he became a surf bum. On the night of the luau, Francie’s father is shocked that her date is not going to pick her up and forbids her to go. Running out of the house in defiance, Francie drives to the beach café where she is to meet Hot Shot and is surprised to find Moondoggie waiting for her. Moondoggie explains that Hot Shot had a previous engagement and turned the job over to him. Upon reaching the luau, Moondoggie asks whom Francie is trying to make jealous, and she lies that it is Kahoona. At midnight, the end of Moondoggie's “shift,” Francie, upset, abruptly leaves and Kahoona asks her for a ride to the beach shack he has borrowed for the night. Although Moondoggie protests, Francie drives off with Kahoona and asks to spend the night with him. Soon after they leave, Francie’s parents come to the luau and learn that their daughter has driven off with an older man. At the beach house, Francie, pretending to be sophisticated, tries to seduce Kahoona, and he plays along with her bluff until he finds himself attracted to her and orders her to leave. As Francie runs out the back door to her car, Moondoggie arrives at the front door and punches Kahoona. Just then the police, summoned by a nosy neighbor, arrive and break up the fight. Kahoona then tells Moondoggie to return to college and warns him that he lacks the affinity for the life of a vagabond. Soon after leaving the shack, Francie’s car has a flat tire and the police pick her up for questioning. At the police station, Francie’s parents are frantic with worry when the officers bring her in. The next day at home, when Francie frets that she will never be a real woman, her mother comforts her with the homily that “a real woman brings out the best in a man.” Frustrated by his daughter’s antics, Russell insists that Francie go out on a date with Jeffrey Mathews, the son of a business colleague. When Jeffrey comes to pick her up, Francie is shocked to discover that Jeffrey Mathews is Moondoggie's real name. Moondoggie drives to the beach to take one last look before returning to college, and there they find Kahoona tearing down his hut. When Francie finds a newly issued pilot’s license with Kahoona’s photo bearing the name Burt Vail, she realizes that he has decided to return to a life of responsibility. Later, after kissing Francie, Moondoggie gives her his fraternity pin.