 Spielberg talks about the test screenings that were held and goes into more   detail about reshooting the Ben Gardner head in the boat scene. He discloses   various ways that the shot was altered and the deciding factor in the used   shot. After telling how that first scream with the new shot was now louder   than the scream they got in the first test screening when the shark first   appears out of the water, that shark appearance only received half the   scream that they got at their first screening. Spielberg reasons that the   audience didnt trust him after the first jolt and were ready for something   to happen when the second scream came around. 