Three explorers investigate the various underwater caves and find the fatal beauty and the values.

Three Korean cave divers with the title “First”!
DH (KIM Daehag) is the first Korean to serve as Full Cave Diving Instructor for nearly a decade in Florida, USA, the Mecca of Cave Diving. Poby (HAN Kilhyung) is a Korean who visited Steve Bogaerts, a world-class underwater cave explorer, learned sidemount cave diving techniques, and was certified as the first Go Side Mount Instructor Trainer in Asia. Scott (KIM Hyoyoung), a former non-commissioned officer of the special forces and the first Korean to be certified as a Tech2 Instructor at Global Underwater Explorers (GUE). With the difficulty of obtaining permission to explore underwater caves in Korea, the three cave divers risk their lives and start exploring unexplored sections of underwater caves on Earth, trusting each other.

Only 5-7% of the total has been explored. Among them, the underwater cave is a place that only humans, not unmanned submarines, can approach at all risks due to its narrow and maze-like structure.
The reason why many scientists are interested in this dangerous underwater cave exploration is that underwater caves are the Earth's time capsules submerged in water and darkness.
It will be the first documentary in which the director himself, who is a cave diver, will team up with three Korean cave divers to share the entire underwater cave exploration process and captures realistic and lively underwater videos without any separate shooting director.