Synopsis：In ancient times, the powerful and noble stored their heirlooms underwater, and future generations could inherit them by presenting the corresponding credentials. Both deposits and withdrawals were conducted underwater, essentially functioning as an underwater bank. From ancient times to the present, this underwater bank has been controlled by three families: the Yi, Ding, and Jiang. To this day, they still operate this trade while remaining hidden among the common people. However, twenty years ago, during a routine "opening of the golden soup," an accident occurred—a giant tentacle suddenly emerged from the lake, nearly wiping out all the skilled members of the three families present, leaving only the young Yi Sa alive. Twenty years later, Yi Sa, now a water demon of the Yi family, begins to experience physical abnormalities. In order to uncover the truth behind the accident and save herself, she teams up with Ding Yudie, a water demon of the Ding family, and Zong Hang, a stranger who stumbles into their world carrying the ancestral tablet of the Jiang family, to dive back into the water and open the golden soup once more.