In the course of the propagation of deep water waves to the shoal water zone, the distribution of the surface elevation and the wave spectrum will be changed due to shoaling effect.

Internal waves happen because the ocean is layered. Deep water is cold, dense, and salty, while shallower water is warmer, lighter, and fresher.

Tsunamis travel as fast as jet aircraft in deep water, where they are spread over a far deeper water column and make for smaller and very gradual waves at the surface.