Early in the film, Ruby and Boake are driving on the beach in his car. There are noticeable mountains in the background. Since the film takes place on the coast of North Carolina, the landscape should be flat with the exception of sand dunes.
The swamp background noise instead of being NC wildlife is jungle noises - Perhaps the same sound clip from Cape Fear with Gregory Peck. Both were to have taken place in the swamps of NC - yet both sounded like something out of Tarzan.