I was listening to Steven Spielberg talk about the making of the movie JAWS. When the mechanical shark was first tested, it operated brilliantly for the first few seconds, but then it failed and sank to the bottom of the ocean. This put the shark out of commission for several weeks. At this point Spielberg couldn’t afford to wait and he was forced to film scenes in which the presence of the shark was implied, but the shark was never actually seen. This then became his motif for the entire movie and he estimates that it probably added $185 million to box office sales. Looking back, he now realizes that had the shark worked properly that first day, the movie wouldn’t have been nearly as effective.