One blustery winter day at a Midwestern university, as undergraduate Merritt Andrews and her colleague Melanie attend a lecture on the dangers of random dating, Merritt asks the teacher to seriously discuss whether a girl should have sex before marriage. Appalled by Merritt's candor, the teacher sends her to Dean Caldwell, who warns Merritt that although her IQ is high, her faltering grades and misconduct in class might be grounds for expulsion. Although she needs to study, Merritt decides to join Melanie and friends Tuggle Carpenter and Angie on their spring break in sunny Fort Lauderdale, Florida, where thousands of college boys and girls go to vacation. As they drive south, the girls pick up hitchhiker TV Thompson, an outlandish dresser to whom tall Tuggle takes an immediate liking, because her only requirement for a date is that he be taller than her. When the girls arrive at the Fairview apartments to find a group of Ivy League boys, or "Yalies," rooming there as well, Melanie quickly entices neighbor Dill into a date. The next day on the beach, Dill spends time alone with Melanie, while TV and Tuggle listen to radio police reports about all the college kids's ridiculous pranks, then go for a drink using a fake ID. Later that evening, after TV laments that he has a hard time interesting women, the sympathetic Tuggle discloses that she likes him but refuses his advances when he suggests they have sex. Meanwhile, Melanie returns home from her date, having asked Dill to keep their lovemaking a secret. The next morning, Melanie grows excited about her prospects with Dill and reminds the girls that a college couple met and got married during their spring break. Merritt corrects her, explaining that though they met over spring break, the couple married only in October just before the girl was due to give birth to their child. Later on the beach, the girls discuss their futures. Tuggle wants to quit school and become a "walking talking baby factory" with TV, while Angie just wants a date. Merritt shows no interest in men until suave Brown University senior Ryder Smith invites her out for a cocktail. On their date, Merritt becomes defensive about her Midwestern background, but Ryder suggests that "sophistication" is how you think about things, not where you come from. Intrigued by his intelligence, Merritt joins the wealthy Ryder on his grandfather's yacht where she explains her classifications for boys: Sweepers try to sweep you off your feet. Strokers use soft caresses to seduce you. Subtles quote erotic literature to entice you. Ryder assumes Merritt speaks from experience, but Merritt fails to tell him that her vast experience dating has been without sex. The next day, an experimental jazz band performs "dialectic jazz" at a bar and offers free beer to anyone who wants to listen. After the band leader, Basil Demotomes, is rejected by both Tuggle and Merritt, he turns to Angie, who is overjoyed to finally have a date. After spending another day together, Ryder tries to convince Merritt that sex is only a matter of everyday "personal relations," but Merritt refuses his advances. That night, a drunken Melanie announces to the girls that she is in love with a new man, Franklin, who is Dill's roommate. The next day, when Melanie recalls that Merritt had supported sex before marriage during the school lecture, Merritt tells her it was not advice for young, drunk kids. Later, Ryder professes that though he has told many women that he "loves" them, he actually likes Merritt. Later that night while the jazz group plays, Angie succeeds in attracting Basil's attention by singing her own catchy lyrics to his composition. Meanwhile, the love struck Melanie finds out that Franklin does not consider their relationship to be special and suggests an impulsive marriage would be silly. The next evening, with only days left in their vacation, Merritt, Tuggle and Angie discuss their chances of getting a marriage proposal without giving up their chastity while they prepare for a triple date together. Despite Merritt's attempts to include her, Melanie insists on staying home to wait for Franklin's call. Ryder takes the group to the Tropical Isle, where a drunken TV cannot resist stage entertainer Lola, who performs underwater acrobatic tricks in a large tank. When TV jumps in the tank with Lola, Tuggle, knowing TV cannot swim, jumps in after him. Soon Merritt, Angie, Ryder and Basil have fallen in the tank attempting to save one another. After the police dismiss the restaurant’s charges against them, the group have a beach party, where TV is once again seduced by Lola's dancing. When jealous Tuggle hears TV use the same line on Lola as he did on her, she interrupts, but TV yells at her to leave them alone. Meanwhile, when Dill arrives to meet Melanie at an arranged motel room and announces he is replacing Franklin, she realizes the boys are using her and tries unsuccessfully to fight him off. Soon after, traumatized by the rape, she calls Tuggle at the motel. Back at the party, Merritt is almost ready to give up her virginity in the heat of passion with Ryder, when Tuggle asks them to help Melanie. As they drive towards the motel from which Melanie has phoned, they see her wandering on the traffic-filled road where she is hit by a car. After Ryder pulls her from traffic, they take Melanie to a hospital, where Merritt chastises Ryder for being like all boys who think girls exist merely to please boys. Alone with Merritt, Melanie laments her mistake and caustically says the boys were not even "Yalies," prompting Merritt to cry in shame. TV arrives at the hospital soon after to reassure Tuggle that he only wants to be by her side. The next day TV, Basil, Angie and Tuggle leave for home, while Merritt remains to care for Melanie until she can return to her parents. Merritt doubts her own resolve about chastity, but Ryder assures her that she is too strong to succumb. Merritt responds that no girl is strong in the face of what she thinks is love. When they both cautiously offer that they might be in love, Ryder asks her to come to his Brown graduation and continue their relationship.