Does the physical weight increase and decrease at the ocean floor as large waves pass ?

That is a very tricky subject. For instance, the speed of the top of the wave is slowed when the bottom is less than one half the distance between wave crests. That's why the crest falls in front of the wave. It's easy to understand that that stirs the sand around, but how exactly does the sand know when it is that distance from the surface? Without a lot of mathematical analysis, we can only say that things move around.