Sand Dunes, Etaples features a view of the inland waterway around Etaples, possibly where the Canches River meets the sea. The heavy white clouds of the summer sky and the way the light plays off the water are typical of his work. Boudin created his skies by splashing a daub of gray onto the canvas and working it thoroughly over and over until he achieved the required effect. Critics with a discerning eye claimed to be able to pick the time of day at which Boudin painted a canvas; so sensitive is his work to the accurate portrayal of light. He painted en plein-air, a practice he encouraged in many of the young artists who came to him for advice, including Claude Monet. The scene is surprisingly busy. Boats sail on the river, while the field in the foreground hosts a number of figures that appear to be working. There is evidence of human activity throughout the painting. The landscape even contains a small hamlet and a windmill.