This is Allen Moe's Sedge Drift at the Museum of Northwest Art in La Conner. Moe makes natural forms out of manufacturing materials. This one's cement. It's a portrait of the curves the water makes in sand on the beach. It's a sculpture that hangs on the wall. It looks more iridescent in person.
Here's a picture I took of sand on a Seattle beach the other day.
And just to make it a whole day of beach art here on Slog (I'm actually out of the office, so I scheduled these in advance in honor of a day off), here's the intersection of designs produced by erosion and designs produced by fingers.