Tsunamis have fascinated since the one in Papua New Guinea in '96 (I think) resulted in such a terrible loss of life. There are lots of theories and models of how a tsunami forms, but I have read some very good ones in New Scientist Magazine. Here's a link to an analysis (in layman's terms) about the Indian Ocean 2005 tsunami. http://www.newscientist.com/article/mg1852...eadly-wave.html
Sometimes these links don't work, so if that's true, I'll cut and paste the article itself if you like.
The understanding of some of the causes of a tsunami can be applied to other sea effects that are more frequently encountered by cruising sailors.
While we were cruising in the Caribbean we spent the "winter" months of January to March in Marigot, St. Martin. Marigot faces north, and a serious concern in the Bahamas and the Caribbean are the terrible northern swells that sometimes come in as a result of strong storms in the North Atlantic. These northers will often create strong high swells that will resonate thousands of miles south until they reach the shallower water of the Bahamas or the shelf off many of the mountainous islands further south. The swells, which aren't particularly noticeable offshore become high, short period swells that become significant waves as they hit shore. For this reason, the French islands and the Bahamas issue alerts for these northern swells whenever a storm in the North Atlantic has raised big seas. It is wise to heed these warnings.
Bahamian ferries and mail boats have been lost in what they call "rage seas" off the northern coast of Eleuthera. I've seen waves across some of the passes in the Abacos that would be terrifying to try to negotiate.
Hurricanes will also raise these monstrous seas, sometimes hundreds of miles from any wind.
It is for this reason that keeping an ear out for weather, even weather that won't reach you, can be a lifesaver.