My example (I tried to encourage the students to use white crayon so it would magically appear when painted over)
The art teacher I was subbing for must really like ocean scenes. She had the kindergarten doing one that was very similar to the fourth grade project. The nicest part was that if compared you could see how a kindergarten student draws the same subject using the same packet of ocean life images for inspiration. All of the students made great drawings, but some did not quite do as tidy a job when they began painting and some painted the fish and the water blue, so it was hard to see what they had drawn. As much as I emphasized the importance of drawing heavily with crayon so the wax/water technique would work, such young students did not always apply enough crayon to get the resist effect. I think it would have worked better with larger drawings (like the middle example), but the drawings were already done the week before and many of them had made lots and lots of tiny fish instead of larger ones.
These are some in progress student examples (look for the white crayon bubbles):