Journalist Bonnie Tsui’s relationship with swimming began before she was born. As she recounts in her fascinating consideration of the practice, her parents met in a Hong Kong swimming pool—a “bikini-clad beauty” and a “bronzed lifeguard.” Why We Swim is divided into five sections, each exploring a reason for humanity’s desire to dive in. There is a section on survival, in which Tsui tells the story of a man now known as “the human seal” because he swam in 28-degree water for six hours after his boat capsized. (Hypothermia should have set in hours before he reached shore, and all his fellow seamen perished.) Tsui also explores well-being, community, competition and, lastly, flow—the state of oneness with water that people find when truly immersed in the rhythms of swimming, something that Tsui and her subjects understand deeply.