Whether it's like the shark in "Jaws" -- if Spielberg's mechanical shark, Bruce, had worked, it would not be remotely as scary; you would have seen it too much.
"죠스"에서의 상어의 예를 볼때 만약 스필버그가 만든 기계 상어인 브루스가 작동했다면 상어가 상당히 많은 장면에서 나타나 겁이 나지 않았을겁니다