The beach after the flags came down

An original description of an invented seaside evening.

By six, the striped flags had been pulled from the sand. Their holes remained in a crooked line, each one collecting a little pool of shadow. The beach still held the shapes of the afternoon: a shallow moat, the ridged base of a bucket, a towel's smooth rectangle surrounded by footprints.

The wind moved along the empty spaces between them. A paper napkin lifted, hesitated and settled against a stone. Farther down, a man folded the last deckchair with the slow care of someone closing a book he knew by heart. Its metal frame gave one thin squeal.

Out at the waterline, the sea was beginning its quiet alterations. It pressed a bright edge into the moat and withdrew. On the next approach, a small wall collapsed. The bucket marks softened. No single wave seemed powerful enough to change anything, yet the beach was steadily losing the day's handwriting.

I stayed until the rectangle left by the towel was difficult to find. The flags would return in the morning, but these particular footprints would not. The beach was not suddenly empty. It was being cleared a little at a time.

How does the writer present the beach changing after visitors have left?