Here is a super easy painting for children.  This was a project I did with kindergarten aged children. I used economical acrylic liquid paint.

 STEP ONE:  Provide two shades of white for the sky and two shades (light and dark) of blue paint for the water.  Let your child swirl them together.   Use red for the boat which is a half moon shape.
 STEP TWO:  Paint a straight line with white paint.
 STEP THREE:  Paint two triangles for the sails with white paint.
 STEP FOUR:  Outline the entire boat and sails in a dark brown paint.
 STEP FIVE:  Optional – using oil pastels, add details.  For waves in water use white oil pastel and make swirls.  For wood on boat use orange oil pastel.  Add sun with yellow oil pastel.