He Came for the Mountains and Seas

When Teng Xin's huge fish tail is raised, it can kill a walrus. But what he is best at is not killing animals, but dragging people into hell in the deep dark water... Teng Xin: "I came for the mountains and seas, and you are destined to die for the mountains and seas." Ruan Lian: "???" If you are sick, treat it. If not, let's make fish soup. The male protagonist is a mermaid, but a domestic mermaid, not a Western fantasy. Intention: Not to accept fate