Upper shoreface
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Upper Shoreface refers to the portion of the seafloor that is shallow enough to be agitated by everyday wave action (wave base).
Water is moved in a circular motion when a wave passes. The radius of the circle of motion for any given water molecule decreases with depth. The maximum depth of influence of a water wave is half the wavelength. Below that depth the water remains stationary as the wave passes. For instance, in a pool of water 1 foot deep, a wave with a 2-foot wavelength would barely be moving the water at the bottom. In the same pool, a wave with a wavelength of 1 foot would not be able to cause water movement on the bottom.
The continuous agitation of the sea floor in the upper shoreface environment results in sediments that are winnowed of the smallest grains, leaving only those grains heavy enough that the water cannot keep them suspended.