i think regular topping off of the sand with fresh sand would be better than putting down a really thick layer to start.
we have heavy clay for native soil. we put down 8" or so of gravel, let that sort of work itself into the clay, which after a month of settlement, the gravel was partially embedded into the clay. then we added the sand, similarly about 8". it then worked itself into the gravel. it is totally sand on top, but it seems to be 'anchored' into the gravel and not washing about as much as i feared.
as you walk deeper into the pond from the beach, the bottom progresses from pure sand, to more gravel, and finally to mostly clay at 4' depth.
the beach itself looks just like that, a beach. here is a pic.
