Isn’t a tsunami a tidal wave? Why don’t we just say tidal wave?
When it's not a tidal surge.
Because there is nothing tidal about a wave generated by a large water displacement. Tidal bores such as the waves on the Amazon and Severn rivers are actual waves caused by the tide coming up a river this could be considered a tidal wave which is much different than a tsunami.
Because it is the pacific ocean not the atlantic.