Tsunamis are ocean waves generated by underwater dis- turbances of the seafloor or by surface impacts and are trig- gered by earthquakes and, less commonly, by landslides, vol- canic eruptions, and meteorite impacts (CLAGUE, BOBROWS- KY, and HUTCHINSON, 2000). These long waves (up to 200 km) travel over the ocean at great velocity. Within the open ocean, the wave height is low, but on reaching shallow water in the vicinity of the coastline, it becomes greatly amplified (BRYANT, 2001). During the process of wave deformation, the height of the wave increases significantly, its velocity de- creases, and as the waves strike the coastline, they often cause widespread flooding across low-lying coastal areas (MURTY, 1977). Our field work suggests that decreasing tsu- nami velocity relies on oceanographic factors such as water depth, shoreface slope, and depth of the tsunami wave base. The 2004 tsunami hit the Phuket western coast around
0938 local time. However, the records from the nearest tide gauge station on Phuket’s eastern coast indicate a delay of nearly 40 minutes before it hit this part of the island.