After leaving diving behind due to a traumatic experience, Im Pa Rang, a former silver medalist, joins the university swimming team. There, he finds himself caught in a complex journey of love and self-discovery with two men, Tae Min and Yu Bin.
The story revolves around Haruka Nanase, a boy who has always loved to be immersed in water, and to swim in it. Before graduating from elementary school, he participated in a swimming tournament along with his fellow swimming club members, Makoto Tachibana, Nagisa Hazuki, and Rin Matsuoka. After achieving victory, each of the boys went their separate ways. Time passed, and in the middle of their uneventful high school lives Rin appears and challenges Haruka to a match, showing Haruka his overwhelming power. Not wanting it to end like this, Haruka, gathers together Makoto and Nagisa once again and brings a new member named Rei Ryugazaki to create the Iwatobi High School Swimming Club in order to defeat Rin.
A man who is suffering a mid-life crisis finds new meaning in his life as part of an all-male, middle-aged, amateur synchronised swimming team.