The beach environment is a dynamic one; barrier islands are essentially "waves" of sand. The waves bring the sand ashore, where prevailing winds blow the sand from the shore to the back side of the island, and the island "rolls", creeping shoreward until it joins the mainland. If you fly over the Florida Panhandle coast, for example, you can clearly see the progression of ancient barrier island against barrier island for several miles inland. Seaward from the barrier island is a series of sanbars, also building and rolling shoreward with the waves, eventually breaking the surface and forming a new barrier island as the old one comes ashore - and so the process continues. Sand is replenished from the mainland, washed to sea in rivers and streams.
Like their desert counterparts, these waves of sand cover and uncover the natural bottom as they move; natural live-bottom reefs come and go with the sandbars.
But it all happens slowly.
When beach restoration/replenishment projects come along they attempt to halt, reverse or to hurry along the natural process, causing perhaps a thousand or more years movement in a month over a localized area - natural processes that would allow a reef community to move along as hard bottom is slowly uncovered and covered don't have time to succeed, leaving sterile rock and sand instead, which may or may not recover in our lifetime.
When I was a boy there were no houses, roads or trash on Florida point. The sand was as white as sugar, and so clean it would "bark" when you walked on it. Sand crabs scurried out of your way as you passed; the water was clear and blue-green, the menhaden so thick they'd get in your bathing suit when you body-surfed, schools of blues & mackerel so thick it looked like you could walk on 'em.
Today....
Wall to wall condos, immigrants from inland.... and dirt.
The sand doesn't bark anymore.
And that hurts.
Rick