 The end of the film differed from the book with the shark simply getting   caught up in cables and drowning. Spielberg changed the ending to get the   audience on its feet cheering. Author Peter Benchley disagreed with the   decision though and told the director that it was a preposterous end that   simply wouldnt happen. Missing here is a short admission by the author that   Spielberg was absolutely correct in his decision to change the ending. 