Let You Survive Under the Sea, and You Rule the Deep Sea?

This is a universe with only water. There is no core under the sea and no planets in the sky. Chaos, deep sea, empty sea, shallow sea, island and land, this is the sandwich that makes up the entire sandbox. Cong Lai was reborn as the bastard son of the Mermaid King. Born just like a human being, he began a difficult journey of survival, upgrading, and climbing towers in the deep sea. Bad news: lots and lots of fish. Good news: There are no nuns in this world. (This book is also called "Rebirth in the Dream of the Fish House as a public servant, and the hairtail fish told me to get out when I don't need it") (PS: I originally wanted to vote for light novels but was thrown to the heavens)