The Horror of Party Beach

A boat dumps a 55-gallon drum labeled 'Danger Radioactive Waste' into the ocean near a small East Coast beach town. The drum opens on the bottom, releasing radioactive contents onto a sunken ship and a nearby skeleton, transforming the skeleton into an aquatic humanoid monster. The monster then heads toward the surface and toward the busy beach where a dance party is underway.

The mutated sea creature emerges and begins moving toward the beach where a dance party by The Del-Aires is in progress. Attendees notice the creature's approach and a wave of unease spreads as people realize something is wrong.

Hank attends the party with his girlfriend Tina, while Hank talks with Dr. Gavin's daughter Elaine. Tina flirts with Mike, the leader of a motorcycle gang, as tensions rise between Hank and Mike. In the end, Tina leaves Hank, turning attention away from him.

Tina swims to a rock jetty seeking privacy, but the monster follows and attacks her, killing her. Her body washes ashore soon after, still covered in blood.

Police enlist Dr. Gavin to help with Tina's death investigation. He proposes Carbon-14 testing to study the tissue's genetic structure, hoping to learn more. Eulabelle, the housekeeper, suggests that voodoo might be behind it.

Elaine confesses her romantic feelings for Hank to her father. She later decides to skip a slumber party with her friends.

The monster, now joined by other creatures apparently born from the same radioactive waste, attacks the slumber party and kills more than twenty attendees. The brutal slaughter triggers panic and a rush to flee or hide.

Three female travelers stop to change a flat tire on a road and are attacked and killed by the monsters. The town remains on edge as more attacks unfold.

While Hank and Elaine are in town for an evening dance, the monster stalks two young women walking through the streets. Frustrated when the women are picked up by a passing car, the monster turns its attention to storefront mannequins, severing its arm in the process.

Dr. Gavin and Hank study the severed arm and identify the tissue as resembling a sea anemone or protozoa. Eulabelle accidentally spills a container of metallic sodium on the arm, killing it and giving them a potential weapon against the monsters.

Two drunken men stumble through town and encounter a dead, mutilated man inside a parked truck; one of the drunks is attacked and killed by a monster shortly after. A montage shows additional women being attacked as the police track the monsters by their radioactive water trail.

Hank drives to New York City to obtain a supply of metallic sodium while Elaine searches a quarry for the monsters. The quarry water tests highly radioactive, and a monster emerges, prompting Elaine to flee while suffering a leg injury.

Gavin arrives with a small amount of sodium and tosses it, killing an approaching monster in a fiery explosion. He engages another in extended hand-to-hand combat. Hank returns with a large supply of sodium, and with police help they destroy the remaining monsters.