Eight years after the devastating 2004 tsunami, British actors Ewan McGregor and Naomi Watts star in a film recounting the tragedy through the eyes of a tourist family caught up in the tidal wave.

But the Spanish director of "The Impossible" insisted that the film -- which starts with a spectacular recreation of the huge wall of water crashing onto a beachfront resort -- is far from a typical "disaster movie."

"Even if the film tells the story in a very direct way, the conclusions it comes to are very complex, more complex than those usual with disaster movies," Juan Antonio Bayona told AFP.

The earthquake-triggered tsunami on December 26, 2004 killed some 230,000 people around the Indian Ocean, including large numbers of tourists caught in the resorts of Thailand and other Southeast Asian nations.

The movie is due out in the United States on December 21 and elsewhere over the next few months. It already opened in Spain and has screened at a number of film festivals, including in Los Angeles.

In the Spanish-financed movie, based on the real story of a Spanish family and filmed in the south of the country, McGregor and Watts play a couple on holiday with their children in Thailand, and separated when the tsunami hits.

"There was something immediately symbolic in the story of this family, which caught my attention when I heard about it for the first time," Bayona said after a November 4 screening at the American Film Institute festival in Hollywood.

After the tsunami crashes ashore and separates them, the seriously injured mother finds herself with her eldest son, while the father played by McGregor manages to save the two youngest children.

The movie portrays the battle for survival amid the havoc wreaked by the wave, from devastated hotels to an over-crowded hospital.

It opens with a family enjoying a luxury holiday in spectacular beach surroundings -- before the wall of water hits.

"When we were looking for funding, the first thing we were told was, if we were going to make the film, we had to see" the catastrophe itself, Bayona said.

"In a film like this about the tsunami, you have to see the monster face to face, and plunge your camera inside it to make filmgoers really feel what it was like to be there."

The young director focused intensely on what the characters are thinking and feeling -- notably the eldest son, played by Tom Holland -- with techniques including unsparing close-ups and omnipresent music.

"The film starts with a shock, in a more documentary style, and as it progresses it takes on a more melodramatic tone... We want people watching to feel emotions as intensely as the characters themselves," Bayona said.

The movie also raises questions about "returning to normal... how do you come back to everyday reality after experiencing something like that?" he added.

But the director did not want to be didactic.

"There is no message, because they weren't given a message. We didn't want to be condescending. We followed them as closely as we could," he said.

Bayona made a name for himself with the unexpected success of his 2007 horror movie "The Orphanage." His new film's US release in December will qualify it, just in time, for next year's Oscars show in February.