As a forming tsunami races across an open ocean, there are few ways to record its passage. Its waves are unnoticed by an ocean vessel among the normal swells of the sea. Its transit is unrecorded by weather satellites that can track the development of even the smallest tropical storm. Its speed allows it to strike a coastline with little or no warning. Tsunamis are such rare phenomena that they are seldom observed directly by scientists. Yet those who do observe the tsunamis-the eyewitnesses who survive the rampaging waters-can provide valuable insight into the wave train's behavior and legacy of destruction.

In a world that is increasingly interconnected, the destruction wrought by tsunamis is becoming better understood with each passing event. Historically, the English-speaking populations of the world have rarely been affected by tsunamis, which may explain the inaccessibility of much of...