A lot of the shots - especially the nighttime ones - used Miley Cyrus's double. Cyrus was still a minor at the time of filming, so the number of hours she was able to work was strictly limited.
Liam Hemsworth's greatest fear was that he would not convince as a beach volleyball player, never having played the sport before and lying about it in his audition.
Tybee Island is a protected landscape. Permission had to be given every time someone had to walk on the dunes. The production found it easier to build their own which were rendered so perfectly and blended in so well with the real natural habitat that they were allowed to remain as part of the terrain after filming had been completed.
Miley Cyrus worked with a dialect coach to help lose her Southern accent. She also learned to play a classical piano.