Chapter Thirteen is the only chapter in the novel that opens with a line of dialogue (" 'You're not putting that thing on my boat,' said Quint."), and so it's as good a place as any to consider Benchley's use of the spoken word. And a good place to start is with the Ten Rules for Good Writing by Elmore Leonard, a master of the art, who uses dialogue over multiple pages to develop character and convey plot. His ten commandments include a couple of "Thou shalt nots" with regard to speech: Never use a verb other than "said" to carry dialogue and Never use an adverb to modify the verb "said". Although Benchley rarely transgresses on these two technical points, he commits far greater sins.
Apart from Quint, whose speech is seasoned with four letter words and profanities, none of the characters possess an identifiable idiolect. Their conversations rarely have the ebb and flow of real speech, and often have to bear the burden of narrative exposition. Sometimes the dialogue seems simply redundant. A case in point is at the beginning of Chapter Thirteen. Hooper's shark cage has been delivered to the dock and - just to make sure we do not assume it's a piece of equipment he normally carries around with him - Benchley describes the vehicle that brought it:
"At the end of the dock a man got into a pickup truck and started the engine, and the truck began to move slowly off down the dirt road.The words stenciled on the door of the truck read: Woods Hole Oceanographic Institute."
A few lines later Hooper describes what the cage is for to Quint: "Divers use them to protect themselves when they're swimming in the open ocean. I had it sent down from Woods Hole - in that truck that just left." At this point you almost expect Quint to reply, "What? You mean that truck with the words Woods Hole Oceanographic Institute stenciled on the door that's beginning to move slowly off down the dirt road?" A couple of pages further on Brody finally confronts Hooper with his suspicions regarding his wife. It should be an emotionally charged moment, but the only energy from the scene comes from the punctuation and the author's liberal use of the exclamation mark:
"Where were you last Wednesday afternoon?"
"Nowhere!" Hooper's temples were throbbing. "Let me go! You're choking me!"
"Where were you?" Brody twisted his fists tighter.
"In a motel! Now let me go!"
"With who?"
"Daisy Wicker."
"Liar! ... Daisy Wicker's a goddam lesbian! What were you doing, knitting?"
As Harrison Ford famously said of Lucas's dialogue in Star Wars, "George, you can type this shit, but you sure as hell can't say it." Of course, Jaws the movie crackles with great lines, but none of them come from the book. Like Casablanca (another troubled production that started shooting without a completed script), almost every scene resonates with a memorable phrase or exchange. Even scenes that require exposition (such as the one played out in front of the defaced billboard or the dinner scene at the Brodys' house) have an energy and rhythm to them.