Coast of South America. Pearl catchers and fishermen are horrified to tell each other stories that a certain "sea devil" has appeared in coastal waters. Believing in the stories of his subordinates, the insidious owner of the pearl mining artel Pedro Zurita decided to catch a fish man in order to force him to mine pearls. Does the sea devil really exist? It turns out that the talented Dr. Salvator really created an amphibious man. His son Ichthyander is the result of successful organ transplant experiments. It can breathe safely underwater because it has shark gills. Ichthyander grew up in the house of a scientist and is completely unfamiliar with the world around him and civilization. He did not see cruelty and does not understand that people do not always bring good and love to each other. Once Ichthyander saves the beautiful Guttiere, who was drowning in the sea, and the whole world turns over...