Sting of Death (1966)

College girl Karen visits her dad, a marine biologist, at his island compound in the Florida Everglades. Her partying friends show up, dance to Neil Sedaka tunes, and taunt the doctor's creepy assistant, Egon. Soon they're victims of a wetsuit-wearing. bipedal jellyfish monster. Jealous of Karen's boyfriend, Egon kidnaps her and carries her to his secret underground lair.