Qian Ting Zong Dong Yuan 8: Di Xin Youji

Douhao, a research submarine fascinated by stories about journeys to the center of the Earth, follows his geologist uncle Tieshihao into the Mariana Trench to investigate a mysterious substance on the seafloor. The expedition goes wildly off course when they are swept into a maze of underwater caves.

Beyond the tunnels lies an enormous hidden world filled with ancient creatures and geological wonders. Douhao and his companions must explore the unfamiliar realm, survive its dangers, and find a route back while discovering that the depths still hold secrets far stranger than the adventures he once imagined.