On the fretted seam between water and land, ocean breakers send a rushing sheet of seawater—a swash—up the beach. The swash receding, pulling seaward with a drag force that takes the sand right out from under your bare feet, every particle felt, is backwash. In The Edge of the Sea, Rachel Carson called the swash zone “a world of force and change and constant motion, where even the sand acquires some of the fluidity of water.”

Ellen Meloy