Deja Vu - how was the suspence created in trailer.

The clip we watched was Déjà vu directed by Tony Scott, he made it look like a happy movie, normal vacation on the ship. However in order to build a false suspense when the child dropped the doll in the sea, and the audience thought that it was a real baby. Although the real suspense was when the man in the parking area was looking around, because he heard the music playing in one of the cars. Non diagetic demonic music builded the tension and shows us that the real action was about to start.