I love to ddo one based on clipper ships. Use several layers of a variety
of blues. Rip carefully in waves, calmer waves, are glued in the back,
rougher in front. Then before all is glued together they cut (scissors)
out a rectangle from brown or whatever for the boat, sails from white,
make the thin masts, black or whatever, sunsets and birds can be added.
Glue all to a light blue or sunset color back. Always a success for my
5th graders. Except, of course if they don't carefully position papers.
Don't give out glue until the whole thing is together.