Obadiah (his real name) is a seventh grade swimmer recovering from a Bad Year (that we don't learn much about, but it involves his gender transition). The Bad Year may be over, but bullies still bully, including his swim coach, necessitating Obie's move to another team. He's lost his best friends Lucy and Clyde anyway, but he's still nervous about starting over with another team. 

Luckily, Obie has a lot of support from his parents, brother, and grandparents, and eventually...a girl he likes.