Deep Down.

A young musician with a talent for all things electrical spies on his sexy neighbor with a penchant for skinny dipping in the pool in broad daylight and her obviously violent husband. He is so violent that in the opening sequence he murders a man for talking with his mouth full of food. As the soft-core sex film advances, she gets involved sexually with the much younger man, all the while luring him into a trap involving the murder of her husband.