The family on which this story is based 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.
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.
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 that she felt very scared and hated the chair for that reason.
The movie was one of the latest produced at the so-called "Ciudad de la Luz" studios (City of Light studios), in Spain. In October 2012, this complex announced its immediate closure due to the small number of productions that took place in the studios.
Lucas, who becomes a hero to his mother and the others in the film, is played by Tom Holland. Tom Holland also appears in the 2016 film, Captain America: Civil War, and the 2017 Spider-Man reboot, Spider-Man: Homecoming, as the titular webslinger himself.