Sting of Death 1966

A young blonde woman in a black bikini lies on a dock in Florida, sunbathing and listening to her transistor radio. She turns it off after hearing a news report about unexplained local murders. Then, without warning, a monstrous hand reaches up from the water and grabs her ankle, dragging her under, where she drowns.

Meanwhile, five of six college friends arrive at the home of Dr. Richardson, the father of one of them, Karen Richardson. [Dr. Richardson] is a marine biologist who studies the “evolution of sea life” with his assistant, Dr. John Hoyt. Karen and the others — Louise, Jessica, Donna, and Susan — are staying at Dr. Richardson’s house. They all wonder why Ruth, who had gotten there earlier, hasn’t joined them on the patio for a cold glass of orange drink.

The mood shifts when a pool party brings a group of rowdy college students to the scene. They taunt Egon, the mildly facially disfigured helper who is secretly in love with Karen. Unfortunately for him, Karen has fallen for John. Yet Egon has his own plan for revenge, and he chooses to act on it by transforming himself into a half-man, half-jellyfish monster. From that moment, he begins to pick off the girls one by one: Ruth is killed while sunbathing; Louise is seriously injured in the pool during the party; Donna dies while being chased through a swamp; Jessica is killed during the search for Donna; and Susan is murdered while taking a shower. The chaos spills into the water as many of the other students die when their boat sinks, and the monster is seen attacking a hull cut through with an axe, as a swarm of Portuguese Man O’ War jellyfish drifts nearby.

Egon forces Karen to swim to his secret laboratory in an underwater cave. There, he reveals an enormous Portuguese Man O’ War imprisoned in an aquarium that is connected to the device powering his transformation. John fatally injures the now-transformed Egon during a fight and rescues Karen. Just as she and John surface, the laboratory machine explodes, finishing off Egon and his evil alter ego.