Continental Crossing

A tsunami engulfed most of the islands on the planet Lingju, leaving only a Ling human named Ganger alive. He had to survive on a raft in the boundless sea, expanding it and subduing pirates. (Prequel) Years later, Ganger drifted to an island where he met an immortal who had taken refuge on Lingju. After passing the immortal's trials, Ganger earned his recognition and, with divine help, was reincarnated with memories of his past life to a place called Hundou Continent to avenge the immortal. A millennium later, due to a catastrophe, he returned to his original homeland... — Description from novelcodex.org