PSacramento....Tsunamis are specifically seismically generated waves, whereas tidal waves more broadly refer large waves or those generated by tidal phenomena (such as tidal bores).
Sad emo....Exactly. There are similar videos of the 2004 tsunami in which the wave intially appears only a foot or less in height. But this is just the leading edge of what really is a highly energetic sea surge of several hundred feet in length that raises the sea level vertically rather quickly (and often higher than the intial wave). It is a wave that doesn't break but just keeps going and going and going. So it may deceptively look inocuous at first but quickly becomes deadly. Also tsunamis come in successive waves, and so people are caught in another tsunami when they come to survey the damage caused by the first wave.
Here is a view of Pagopago airport while the waters were receding between surges: