Try Not to Think About It
Its best if you don't spend too much time trying to figure out the whys and wherefores of fantasy and science fiction worlds. They are what they are for a reason.
When you watch a western, you can look for realism. That makes sense. The movie is grounded in a genre that is real. The cowboys rode horses. The Cheyenne had large war bonnets. The trains belched smoke. But no one had giant mechanical spiders that they used to terrorize a community with (we're looking at you Wild Wild West). A little research in any number of books on dress and society can yield a vibrant field of exciting genre fiction.
Its different on the other side of the tracks.
In movies like Star Wars, or shows like the Walking Dead, the authors don't have to ground anything in realism. A little is good, but too much spoils the fun. Midi-chlorians were used to explain the force in the prequels. People were not thrilled with it (well the vocal ones were not). It took the mystical away form the Force and made it scientific...it explained the magic trick. And the magic trick was a little less magic after that. But none of it was necessary, no one really questioned what the force was. It was the Force.
Subtle explanation is better. When you watch the Walking Dead the characters don't seem to understand the world of the zombie...shoot them in the head you say! But from what I understand there are no zombies in pre-walker culture. There is no concept of the undead. So no one would know what to do. But this is never explained in the show. It doesn't matter. It doesn't need to be. Just leave it alone. Try not to think about it.
And that's really the rub here. Jaws was a horror movie. It wasn't a nature documentary. Sharks don't have the capacity to recognize people and hunt them individually (its more random, like in Sharknado). They have very limited emotional responses if at all. Jaws is a horror movie. Try not to think about it.
In short, whether creating or watching, try not to think too much about it. Just slip into the moment and run with Rick and crew from the walkers, or life the X-wing fighter out of the swap or swim like a mothers-son-of-a-bitch to get away from that shark!