Thompson on Hollywood

Scanline VFX (300, 2012) and VFX supervisor Michael Owens lavished so much time and energy on the nine-minute tsunami at the start of Clint Eastwood's Hereafter that the movie won the Visual Effects Society (VES) award for outstanding supporting visual effects in a feature motion picture as well as a hotly contested spot in the final VFX Oscar five.

Here's a video breakdown showing how they did it:

For more details, see this VFX feature.