The family on which this story is based upon were present during the whole shooting process. They were giving tips, especially 'Maria Belon' who is portrayed by Naomi Watts. The whole family also attended the film's premiere at the Toronto Film Festival in 2012.
For the underwater scenes, Naomi Watts was strapped in a rotating chair. While filming, Watts couldn't hold her breath any longer and she gave the 'stop' sign. Instead of stopping, the chair started spinning the other way around. Later it was revealed that it was a technical error and Watts stated the she felt very scared and hated the chair for that reason.
The crew filmed partially on location at the actual resort, since rebuilt, where the Belon family was vacationing when the tsunami hit. For the tsunami destruction scenes, a scaled model of the resort was used.
This movie has been one of the latest produced at the so called "Ciudad de la Luz" studios (City of Light studios), in Spain. At October 2012 this complex announced its immediate closure due to the small number of productions that have taken place in the studios.