Having previously survived being riddled with bullets, the Gill-man is captured and sent to the Ocean Harbor Oceanarium in Florida, where he is studied by animal psychologist Professor Clete Ferguson (John Agar) and ichthyology student Helen Dobson (Lori Nelson).
Efter at have overlevet at blive gennemhullet af kugler, bliver Gill-man (Dyret) fanget og sendt til Ocean Harbor Oceanarium i Florida, hvor han bliver undersøgt af dyre-psykologen Professor Clete Ferguson (John Agar) og den iktyologstuderende Helen Dobson (Lori Nelson).