When a doomsday rainstorm floods the world, Li Shengwen bets his life and transforms into a mermaid in exchange for his mother's Ark ticket. Five years later, his younger brother Lin Zhisheng drew his gun from the underwater city and set out to fight, but he ran into his half-human, half-fish brother deep in the ruins - his tail fin was ulcerated and oozing with strange black mist, and he also hid the shocking secret of "alien water stealing the earth".
Purpose: Survival in the apocalypse