"Forbidden Land of the Underworld" is adapted from Pan Haigen's popular novel of the same name. It is the first marine adventure series IP in China and the first IP project to show the legendary life of the mysterious "sea salvagers" Tanka people on the water. The film is based on the theme of adventure and treasure hunting, integrating various hot elements such as sailing, adventure, and monsters. It revolves around the mystery of the underwater city and tells the various adventures experienced by Bian Haisheng, a descendant of the Tanka people, An Su, the daughter of the owner of Lingyao Island, and others in the process of exploring the underwater city from the sea.