All wave analysis is out the window in deep water, and there's multitudes of wavelengths and ampitudes and directions.
Basically, upon hitting a slowly rising bottom to shallows, the wave bottom is dragged, the pressure distribution is shifted as water flows back off the beach, it rises and may crest or break. It's attempting to keep it's deep water profile as the water gets shallower.
A waveform hitting a vertical wall, like a cliff or coral reef escarpment, it's bottom is reflected away, leaving little to support the top, which mellows away. The critical thing to remember is the water isn't moving horizontally in the deep wave, it moves a distance only as thick as the wave is, then every atom of water has landed almost exactly where it was before the wave got there.
You may think "well, i can't chop the bottoms off like a reef, but i can chop the tops off, and that will be as good!", and you'd be half correct. One such machine was built, with two problems i recall: 1) the 100's of flapper valves wore out very fast, 2) they could not get the water off the top of the machine fast enough (the existing water stopped new waves tops from boarding the machine, by keeping the flapper valves closed).
Think also of a flag in a steady breeze. The flag doesn't leave the flag pole, but the wind makes pressure waves (ripples) that run the length of the flag and fall off. But every atom of the cloth is exactly the same place between waves.