Draw a countinous line with a black crayon. Starting on one side of the page, draw a line that is going on a curvy walk. You want the lines to crisscross to make medium to large shapes.
Use watercolor paint to fill in the shapes you made.
Notes
When drawing a line with young children, have them add a dot on both sides so they know they need to connect the dots with the curvy line.
If painting, paint shapes that are not touching first. This will help stop the color bleeding into each other.