The Porn Queens.

Four actors on film are lost from the crew. They are on a boat in the middle of a dam. They land at a strange point, where they meet a tribe of semi-savages and backwards in time. They are imprisoned and learn of the existence of a scientist who was experimenting with human guinea pigs, brain transplants, crossings of humans with animals, etc. there. Pan, half man and half goat, a figure from Greek mythology, is the leader of the band, who hypnotizes everyone with the touch of his flute. He seizes the women and traps the men, making the women of the tribe fight over them.