Building a retaining wall by the shore

Down by the beach, where my dock is, the shoreline is washing away.  So I went to the town and got a permit to build a retaining wall.  I got a heck of a deal on some granite and a friend of mine said he’d deliver it for free.  I have my own tractor so I’m going to be able to move all of the granite down by the water and place it myself.  It’s going to take me a couple of weekends to build.