Synopsis: The series centres on the love story of Shim Cheong (Jun Ji-hyun), a mermaid, and Heo Joon-jae (Lee Min-ho), a witty con-artist. Focusing on rebirth, fate, and unrequited love, their tale is juxtaposed with the parallel story of their Joseon-era incarnations, the mermaid, Se-hwa, and town head, Kim Dam-ryeong.