Todd Arliss is a selfish Olympic swimmer who, seeking public acclaim, attempts to rescue a drowning man and damages his spinal cord when waves push him into a ship. Desperate to regain his swimming ability, Arliss willingly participates in an experiment by the scientist Doctor Dorcas who "cures" his injured back by blending his DNA with that of hero Namor the Sub-Mariner and a tiger shark. Although successful, the process changed Arliss both physically and mentally, endowing him with razor-sharp teeth and gills and making him savage and predatory.