The way tsunamis affect different locations is quite interesting! The wave length (distance between two peaks/troughs) at sea can be hundreds of kilometers long, a tsunami could pass under your tiny boat while out at sea and you wouldn't even notice it. It's only as they approach land that the shallow depths force the wavelength to shorten, forming the giant waves we usually associate with tsunamis.
[1] http://www2.scholastic.com/content/images/articles/sn_ts/sn_...