Here is a video that shows you the size (height) of the wave that came in. Did this inundate the reactor complex to the same extent? Yikes. No wonder we're talking about possible containment damage. That was an immense mass of water.
Video: http://www.youtube.com/watch?v=xOfy1CoxrMo
Video: http://www.youtube.com/watch?v=xOfy1CoxrMo