The drama is based on a manhwa with the same title. Tamna the Island is set in 17th-century Joseon times as a young English castaway, William (Pierre Deporte), comes to the island and meets Jang Beo Jin (Seo Woo), Park Kyu (Im Joo Hwan), and Yan (Lee Sun Ho). The name "Tamna" refers to what is now called Jeju.
(Source: DramaWiki)