Tales of Horror #2

An architect loses his secretary, who he's secretly in love with, to a young good looking man. Wanting revenge on the couple he offers them a huge mansion complete with a beautiful swimming pool as a gift. It turn out that inside the pool is a prehistoric furry tentacled monster. The architect encountered this monster years ago in a small watering hole and built the swimming pool over the hole to destroy the couple. Unfortunately for him the monster also makes him a victim.