In a secret territory off the coast of Huaxia lies an ancient underwater civilization with a history stretching back ten thousand years: the Canglan Sea Clan. They command vast stretches of deep-sea territory, wield extraordinary strength, and possess supernatural technology and powers far beyond anything found on land. For generations, they have ruled the four seas. Years ago, their revered leader, Hai Yue, grew weary of the ruthless power struggles and suffocating restrictions imposed by the underwater clans. She broke through the deep-sea barrier and fled the clan's royal city. At the coastal border, she met Tang Cheng, a kindhearted lighthouse keeper devoted to his post. They fell in love at first sight, overcame the divide between land and sea, and made a home together in a seaside town, where they had a half-blood son, Tang Yuan. Their peaceful happiness was short-lived. Pursuers from the Canglan Sea Clan tracked them down. To protect her husband and young son, Hai Yue painfully gave up her life on land and was forced to return to the depths to face punishment under clan law. In the end, she was exiled to a lightless abyss teeming with monstrous beasts, where every member of the clan believed she had perished.
From birth, the half-blood boy Tang Yuan displayed extraordinary abilities and an affinity for the deep sea far beyond that of ordinary people. He could breathe freely underwater, move at incredible speed, and communicate with the sea creatures of all four oceans, even sharing an understanding with all kinds of marine beasts. Hai Qi, a loyal elder of the Canglan Sea Clan, secretly found Tang Yuan and lived in hiding by the coast for years, teaching him the clan's secret arts, skills for surviving in the deep sea, and the ancient history of the oceans. In silence, he entrusted Tang Yuan with the responsibility of maintaining the balance between land and sea and safeguarding peace across the four oceans. As an adult, Tang Yuan continued to live on land, keeping a low profile as an ordinary man while quietly protecting the coastal people. Time and again, he used his extraordinary abilities to avert maritime disasters, including tsunamis, shipwrecks, and attacks by monstrous beasts,
