How high was the 2004 tsunami?

Question

I've heard around 20 ft, but the Banzai Pipeline in Oahu is around that big, maybe more.

Answer 1

In deep water, the wavelength of the swell that produces the surf at Oahu is at least three orders of magnitude less than the wavelength of a tsunami.  What that means is that there is a lot less water moving forward for surf than a tsunami.  Less water means less run-up, or distance onshore the wave propagates.  The 2004 tsunami was huge, the leading edge may have initially vaguely resembled a nicely formed plunging breaker, but behind it was a nearly flat mass of roiling water as high as the leading crest.  More likely as it came ashore in Banda Aceh, it looked less like a plunging wave and more like a vast advancing tidal bore.  Video of it striking Phuket and Sri Lanka show it as a quickly rising tide than a huge surf-able wave.  

There is no comparison between the energy of surf and the energy in a tsunami.