Shark''s death

It was some sort of electrical device (looked kinda like an underwater camera) that was rigged to send out electrical impulses and drive the shark crazy. While it was doing this, they drove the boat directly towards the shark, spearing it with the boat's prow just as it was leaping out of the water in a fit.

In the original version, once the shark is speared, it bleeds heavily, dies, and sinks along with the damaged boat while others swim to safety. Only test audiences didn't like that death scene, so the theatrical cut featured the shark exploding (using a combination of reused footage from the first film and footage of a toy shark exploding in a bathtub) after it was speared, which of course, makes no sense. They also made Jake live, with further adds to the implausibility.