Tsunamis are only a foot or two in height because they are so long. They only get huge when they hit shallow water and begin to back-up on themselves.

They break up and dissipate when they start feeling the bottom. They don't last that long. They don't travel that far, but they can bust up everything [in their path].

It was very fortuitous for our moorings to be installed right in the path of Ivan. From theses measurements we have learned that waves over 90 feet are not rogue waves , but are actually fairly common in hurricanes.