Isabel / “Belly”
Belly is our first-person narrator and protagonist of the story. This is the year that Belly turns sixteen, and coincidentally has had a mini makeover and become "pretty." Through flashbacks, Belly shares that she has always felt excluded from the games of Conrad, Jeremiah, and Steven, both because she was a girl and because she was younger. This summer, she finally feels like the Fishers and other characters at Cousins Beach are seeing her as more than their "little sister."
Laurel
Laurel is Belly's mother, and the reason why Belly gets to spend each summer at the Cousins Beach house: Laurel and Susannah are old friends, and have been spending summers together at Susannah's childhood home for longer than Belly has been alive. Belly describes Laurel as unfeelingly rational, but throughout the novel, she demonstrates a quiet, caring affection towards her children.
Steven
Steven is Belly's older brother, and a good friend of Conrad and Jeremiah's. In big-brotherly fashion, he bullies Belly here and there. He leaves Cousins Beach early to go on a college tour with his father.
Susannah
Susannah Fisher is Laurel's longtime best friend and the mother of Conrad and Jeremiah Fisher. She is a housewife married to Adam Fisher, and is described as warm, loving, generous, and at times, stubborn. Belly and Susannah have a close, emotional relationship, unlike Belly's relationship to her own mother. Susannah is convinced that Belly is destined to marry one of her sons. Near the end of the novel, it is revealed that Susannah's cancer has returned, and that she will likely not survive this time.
Adam
Adam Fisher is the boys' father. He works as a banker and thus does not come to stay at Cousins Beach with the rest of the family. He never makes an appearance in the novel, but is described by Belly in reference to past interactions and a phone call. She feels that he is hard, distant, and somewhat militant in his parenting of his children, wishing for them to fit a certain mold in which they play football and go fishing. She finds out that he is divorcing Susannah while she has cancer, a fact that upsets her.
Conrad
Conrad is Susannah's older son. Belly has had a crush on him for many summers: “Conrad was the older one by a year and a half…unattainable, unavailable.” Though she falls in love with him for his sincerity and kindness, Belly finds that this summer, Conrad has been acting strangely, being prone to mood swings and having started to smoke cigarettes and drink copiously.
Jeremiah
Jeremiah is Conrad's younger brother. Whereas Conrad is a somewhat brooding figure, Jeremiah is comfortable being the center of attention and is openly affectionate with friends and family alike. Jeremiah and Belly share a close friendship, but this summer, he expresses the desire to turn their friendship into something more.
Cam
Cam is another of Belly's romantic interests. The two meet at a Fourth of July bonfire, and realize that they both attended a Latin competition in their childhood. The two quickly bond and start going on dates. He is the first person that Belly really dates, but she soon finds her interest fading as they discover various incompatibilities in taste and philosophies of life.
Taylor
Taylor is Belly's best friend from school. Described by Belly as a vain, self-absorbed, and jealous but pretty person, Taylor represents, for childhood Belly, an aesthetic ideal. One summer, she brings Taylor along to Cousins Beach: Taylor promptly tries to make moves on every boy in the house, succeeding in kissing both Jeremiah and Steven. Both Belly and Jeremiah reflect that Taylor has made a mess of things. Belly reflects that that summer changed her relationship with Taylor, but that they still remained friends.
Nicole
Nicole, or "Red Sox girl" as Belly names her in her head, is an older girl that Belly sees with Conrad. The two are implied to have some kind of romantic relationship, which Belly envies. Nicole is also described as being unkind to Belly in various moments.
