Reply #5: here's from BBC news

[barb162]

Wave goodbye

Tsunamis aren't like wind-generated waves that rhythmically roll onto a beach. A tsunami can have a wavelength (ie distance between wave crests) in excess of 60 miles (100km) and there may be an hour between them. They travel at great speeds across an ocean with hardly any energy losses and are barely noticeable out at sea.

Over the deep Pacific Ocean, a tsunami travels at about 500mph (800kph). If an earthquake happened in Los Angeles, a tsunami could hit Tokyo quicker than you could fly between the cities by jet.

Shallow water slows the tsunami and its height grows. Tsunamis batter the coast with tremendous amounts of energy. They can strip sand from beaches, tearing up trees, and even obliterating whole towns. Some have been known to reach as much as 30m above sea level. Hardly the perfect conditions for paddling.