On the coastal material, change the "Scatter" parameter to a texture and create a new texture. Then change the "MonoFractal" to "BreakWave Scatter". Set all the parameters to the same value or texture as for the "Displacement" parameter.
Do you like the result? I don't. Maybe the damping should be faster. Set it to 7.5 to try.
Yes, this is better. Check it at the beach level:
That's it!