Teenage friends Will McKenzie, Simon Cooper, Jay Cartwright, and Neil Sutherland have finished their A-levels and are about to leave Rudge Park Comprehensive, much to the relief of Mr. Gilbert, their sardonic sixth form tutor. Within their final week of school, Jay's grandfather dies, Simon is dumped by his girlfriend Carli D'Amato, and Will's divorced father tells him he has married his much younger mistress. The boys decide to go on holiday together and Neil books them a trip to Malia, Crete.
At a bar, they meet four girls: Alison, Lucy, Lisa and Jane. Their initial meeting does not go smoothly, but the girls arrange to meet the boys at their hotel the next day. Outside the bar, Simon sees Carli across the street and talks awkwardly with her before being knocked down by a quad-bike ridden by James, a cocky and abusive bully and alpha male club rep and Carli's new boyfriend. She reveals she is going to an all-day boat party later in the week, and Simon pledges to meet her there.
The next day, Jay and Simon get into an argument over Simon's continuing obsession with Carli and Jay's continual false bravado and they brawl in the street until Will and Neil drag off Simon and Jay, respectively, in different directions. Desperate to buy a ticket for the boat party, Simon naively sells all his clothes to James, including what he is wearing, but receives no money for it. Meanwhile, Jay angrily tears up two of the four boat party tickets he secretly bought for all of them while drunk the night before as a surprise. Jay and Neil encounter James and his friends in a bar and they try to join in and befriend them but James rejects them and verbally abuses them both and threatens to injure Jay if they don't leave which makes Jay cry. Later that evening, the four boys meet back at the empty bar and reconcile. The girls then turn up and suggest that they all go skinny dipping at the local beach. Jane attempts to kiss Jay, but when two men poke fun at him over her weight and Jay pulls away, she leaves him behind. Will has better luck with Alison until she spots her boyfriend, Nicos, having sex with another woman, and she leaves crying. In the water, Lucy and Simon appear to be growing closer, and are about to kiss, but Simon sees Carli on the beach and leaves Lucy alone in the sea.
The next day, they meet the girls again at the beach. Alison gives Will Nicos' ticket, while Simon apologises to Lucy, and she offers him her boat party ticket so that he can be with Carli. On board, Simon witnesses an argument between Carli and James. Carli then kisses Simon passionately, and he is elated, until he realises that she is just using him to make James jealous. Finally seeing Carli for what she really is, he ditches her. Meanwhile, Jay apologises to Jane and they form a relationship as do Will and Alison and Neil and Lisa. later Jay and Jane run into James who mockingly makes fun of Janes weight and demands a 20 euro note off Jay so that he can snort drugs. Jay gets his own back on him by taking a note that was secretly concealed in his anus and gives it to James. James then snorts cocaine unknowingly walking around with the feces sticking out of his nose causing the girls he flirts with to move away from him in disgust much to his confusion. Simon finally sees that Lucy is more worthy of his attention than the shallow Carli, and knowing that he has been less than kind to her, he decides to swim to shore as a grand romantic gesture, but he struggles and almost drowns. As he is loaded into an ambulance, Lucy kisses him and they reconcile. After the boat party is over, the other boys and girls visit Simon in hospital, and once he recovers they all spend the rest of their holiday together as couples. In a final scene before the credits, a drunken Mr. Gilbert is seen riding a quad bike through the streets of Malia in his underwear with a tie round his head in a John Rambo style.