Ingrid Coleman writes letters to her husband, Gil, about the truth of their marriage, but instead of giving them to him, she hides them in the thousands of books he has collected over the years. When Ingrid has written her final letter she disappears from a Dorset beach, leaving behind her beautiful but dilapidated house by the sea, her husband, and her two daughters, Flora and Nan.

Twelve years later, Gil thinks he sees Ingrid from a bookshop window, but he's getting older and this unlikely sighting is chalked up to senility. Flora, who has never believed her mother drowned, returns home to care for her father and to try to finally discover what happened to Ingrid. But what Flora doesn't realize is that the answers to her questions are hidden in the books that surround her. Scandalous and whip-smart, Swimming Lessons holds the Coleman family up to the light, exposing the mysterious truths of a passionate and troubled marriage.