Desharow, a marine biology student obsessed with merfolk, finally gets his chance to study them up close when his mentor, Rhein, takes him on a research expedition. The team soon captures a mysterious black-tailed merman from a species known to be highly dangerous. The powerful and beautiful creature instantly captivates Desharow, who becomes willing to risk everything for the sake of research. Drawn in by the merman's mesmerizing features and otherworldly allure, Desharow fails to realize a crucial truth: he has already become the predator's chosen prey.