The examination of the remains of Chrissie Watkins establishes the point of Matt Hooper. Up until now he has been a smart alec frat boy in a grown-up world. Yet once the action switches to Brody and the Medical Examiner leading him into the autopsy room, the ichthyologist comes into his own.

For a start, he is dictating details into a snazzy ‘70s headset microphone that predates Madonna by some twenty years. After the medical examiner pulls back the sheet to reveal Chrissie’s remains — Dreyfuss’ little bit of hyperventilating is a thing of beauty — Hooper cleans his glasses (they are clean, we have just seen him do this in the harbour: it’s a statement of concentration) and warms to his task: he launches into a litany of medical jargon (a “mid-thorax” here, a “partially denuded bone” there), Latin fish-speak (a single sentence contains “squalus”, “unjumanus” and “Isurus Glaucous”), all the while controlling the room and growing in confidence, be it getting the medical examiner to fetch him water (Dreyfuss does a great sloosh) or keeping the air hygienic (“DO NOT SMOKE IN HERE. THANK YOU VERY MUCH.”).

To top it all, in the scene’s most famous dialogue, he displays a knowledge of London serial killers circa 1880: “Well this is not a boat accident! It wasn't any propeller! It wasn't any coral reef! And it wasn't Jack the Ripper! (here Dreyfuss splashes water on his face for added dramatic pause) It was a shark.” A frat boy has become a man.

More than anything else in Jaws, the autopsy smacks of Spielberg’s TV days, covering the action in basically two set-ups and graced with perhaps the ugliest shadows in Spielberg’s career. Still the director manages to elevate the blocking from just a regular bread and butter scene. Firstly, he places Hooper centre stage but puts Brody and the Medical Examiner at either end of the room, Brody backlit against a window, the shameful M.E. (who has changed his view from a shark attack to a boating accident) almost blending into the wall, a bland man against a bland background. To give the scene added visual lift there is a lovely use of the arc of the lab lamp to almost provide a proscenium arch in the frame.

Yet the strangest moment of the scene is the close up cutaway of Chrissie’s severed arm accompanied by Hooper’s line, “So this is what happens.”

As Spielberg explained (from a question by Bryan Singer) to Empire in the 20th birthday issue, “I had cut out a line of dialogue and inside the line of dialogue I artificially manufactured a new line. Verna Fields and I pieced together ‘This is what happens’ from other things that he was saying.” Yet it doesn’t fully explain the significance of the line Spielberg manufactured or why the line was changed. Some viewers recall the line “This is what happens when a young girl goes swimming.” Jaws forum dwellers suggest it is an added-in later cutaway and then it might be the prop man holding the severed fore-arm. Either way, from The Shining to Reservoir Dogs, many of masterpieces have an in-built conundrum, a mystery that enriches the experience. This is Jaws’.