How can a mermaid from the Joseon era survive in modern-day Seoul? Shim Chung (Jun Ji Hyun) is a mermaid who finds herself transplanted to modern times. She is caught by Heo Joon Jae (Lee Min Ho), a charming but cold con artist who is the doppelgänger for Kim Moon, the son of a nobleman from the Joseon Dynasty. But in the present time, Joon Jae works with Jo Nam Doo (Lee Hee Joon), a skilled conman who guides Joon Jae to become a genius scammer. But Joon Jae’s friend, Cha Shi Ah (Shin Hye Sun), who works as a researcher at KAIST, may be Chung’s only hope for surviving in her strange new world. The story is inspired by a historical tale about a mermaid contained in a short story anthology known as “Eou Yadam” by Joseon-era scholar Yu Mong In. This drama marks the last acting role for superstar Lee Min Ho before he enters his mandatory two-year military service and the first acting role for Jun Ji Hyun after giving birth to her first child. Parts of the drama series were filmed on the Pacific island of Palau and in Spain.