Jaws is famous for not showing the shark much, but images of sharkdom are never off the screen for long. Brody pores over books filled with pictures of sharks, shark fossils, shark paintings, shark teeth, shark bites, etc. Quint's boat, the Orca, has shark jaws mounted on the front, and his boathouse is chock-full of them—remember the great scene in which the Orca is viewed through a shark's jaw? (Orcas, by the way, are great white sharks' only natural predators.) Even the Amity community buys into shark mania, selling souvenir shark teeth, photos, arcade games… the works.
After that first scene where Chrissie is killed by some unseen denizen of the deep, even just a shot of the surface of the ocean forces the audience to think about what's underneath. As one writer put it, "We see things that indicate the monster is around or act as the monster by proxy. Turning simple things into nightmares. A shadow, a wave, a dock, a barrel. These things can't kill anyone, but the thing near it, that's pulling it along, what it could be—that's the real danger" (source).
Of course, a shot from beneath the water is an even bigger signal that the shark is near. And if that music starts playing? Fuggettaboutit. We almost start screaming, "Get outta the water!" at the screen involuntarily. All of these sharky things symbolize the shark and keep the audience's mind on it even when it's not in the picture.
Shark biologists have long bemoaned the anti-shark attitudes, and even shark killings, that followed the release of Jaws. They point out that the idea of "territoriality" is a myth and that sharks really don't find humans all that delicious; we're too skinny. Typically, they'll take a bite and look for something else on the menu. When they do kill people, it's usually a bull shark, not a great white. Furthermore, sharks tend not to hold personal grudges. Maybe great white sharks did get a bad rap in the novel and the movie. Even Jaws author Robert Benchley came to believe that.
So, there's no reason to fear these maligned, misunderstood creatures.