Watercolor. The process for this one's kinda interesting. I covered the paper with water, then used a wide, soft brush to add vertical streaks of color. I let it dry just a little bit so it was damp but not wet, then with the same brush, using only water and no pigment, made long horizontal strokes through the damp paint. The colors were mixed together in the strokes, creating the sand.  For all of the process I've explained so far, I was mostly just playing about with my colors, not trying to make something specific.
I let the results dry completely, then decided to add the figure walking. The process for the person was closer to my usual methods, just laying down a silhouette and building the colors from there. I painted in the bird later for some added interest.