One year after the events of One Breath, Kaia Cayden and her Gilled One boyfriend, Prince Olv Atlon meet Yuki Ruki, an ex-surfer from Okinawa with a deep affinity for the water...and lingering trauma that led to her becoming a double amputee. Moving into Ark Epsilion, Yuki and Kaia share their past, treasures and troubles alike and quickly become friends. Before long, they decide to strike a deal.

Kaia and Olv band together to help the struggling Yuki learn to love the water once again, in another daring underwater adventure that will have you holding your breath with them!