In producing the movie Poltergeist, Steven Spielberg employed the structure that worked for him in Jaws. In the latter movie, there is an Everyman, Sheriff Brody (Roy Scheider), and his family, corresponding to Diane Freeling (JoBeth Williams) and her family in the former. The shark is a monstrous creature terrorizing Amity Island just as the demons terrorize the Freeling household. In Jaws, we have the mayor who lets the expected revenue from tourism jeopardize the safety of those who plan to swim in the ocean, while in Poltergeist, Steve Freeling’s boss jeopardizes the safety of the Freeling house and the entire neighborhood in an effort to save money by not moving the bodies of a cemetery before building houses on top of them.
Once the shark proves to be too menacing to ignore, a scientist, Matt Hooper (Richard Dreyfuss), is called in from the Oceanographic Institute, just as three parapsychologists are called in to investigate the weird happenings in the Freeling house (one gets the feeling they inspired the movie Ghostbusters (1984)). But science alone cannot do the job. Therefore, someone with personal, practical experience is needed. In Jaws, this takes the form of Quint (Robert Shaw), an old salt who has been a sailor all his life and has dealt with sharks many times. In Poltergeist, we have Tangina (Zelda Rubinstein), a woman with psychic powers, who knows how the other world operates.
Ultimately, however, it is Everyman Brody who kills the shark, when science and practical experience fail, just as Diane must save her children herself after the parapsychologists and the psychic have failed to completely do the job.
Unfortunately, the final attack by the demons after everyone thinks it is safe is a little too much. It would be like having the shark make one more attack after Brody thought he had finally killed it.