I used to be a fish. But I didn't like swimming anymore. So I grew some legs. Inspired by a pet fish and fueled by imagination, a boy tells a whimsical version of his own life story, which mirrors the process of human evolution. Simple, surprising, and innovative, Tom Sullivan's debut is both a light introduction to science and a tribute to every child's power to transform their lives and to dream big. From debut author-illustrator Tom Sullivan comes a surprising and innovative picture book that is both a light introduction to the science of evolution and a tribute to every child's power to dream big. In I Used to be a Fish, a boy is inspired by a pet fish and fueled by imagination to tell a whimsical version of his own life story, which mirrors the process of human evolution. Children-and adults-will love the Seussian absurdity of this tale.

The book features a timeline of life on earth and an author's note, which includes important facts about evolution.