The scene where the tsunami hits the resort could only be filmed once. It would have cost too much money to rebuild the set.
Many of the extras were actual survivors of the tsunami.
According to Naomi Watts, the producers of the film heard an interview on Spanish radio where the family told their story of surviving the Tsunami and decided to make a film based on it.
It took a year to put together the ten-minute sequence, a recreation of the moment the wave came crashing down on the luxury hotel in Khao Lak.
The crew filmed partially on location at the actual resort, since rebuilt, where the Belon family was holidaying when the tsunami hit. For the tsunami destruction scenes, a scaled model of the resort was used.