The basic things needed for sand is: Rock and Energy. Rock from the Shoreline and energy from the waves.
    Waves are made from wind and movement in the ocean. The wind comes from the summer time hurricanes that as you probably know, make a lot of wind. So basically the harder the hurricane, the harder the wind and harder the waves.
     
    Sand is made from these hard waves that will go above the rocks and crash down, grinding them in to sand. Another result of waves and water, there are small shore rocks that have been severed from the shore, as a result of water weathering (Mechanical Weathering).

    One more thing is where water caves come from. The caves are a result of water constantly driving into the cliffs. For example, you have a hose, you point it down to the ground and concentrate it on one spot, after your done you notice a hole in the ground. That is water erosion and weathering in a nut shell.