The production of "Jaws" offered a myriad of technical difficulties that threatened to bury the picture before it ever got made. Producers Richard D Zanuck and David Brown both read the book in one night, upon which they decided to proceed with the picture. This impulsive decision got "Jaws" off the starting blocks before practicality could ground it.
Although the shark doesn't command a great deal of screen time, its appearances, however fleeting, had to be believable. The first shark simply sank to the bottom of the sea before anything could be filmed. Once they'd managed to refloat the beast they were forced to perform take after take to make it do anything. Time and time again it failed with the usual result of it looking just plain stupid. Watching these outtakes you realise just how effective the editing is as it is that same goofy rubber shark that terrifies in the film.
Real shark footage was also used and one scene, where a shark attacks a diving cage, was captured by sheer luck. A shark happened to get its nose stuck in the cage and the resultant wild thrashing was captured and used in the movie. The footage above water when this happened is simply terrifying.
The time limit on production resulted in Spielberg shooting a scene in the editor's swimming pool with the giant shark so that he could complete a scene as he had originally envisioned it. This combined with all the other problems the shoot encountered, including the sinking of the 'Orca' boat, certainly makes the final result very impressive.