Use colored construction paper, crayons or markers to make a sand-colored ocean floor inside a shoebox. Color the rest of the box blue. Bend green and orange pipe cleaners to make seaweed and coral. Glue these so they stand upright from the ocean floor. Scatter paper or plastic star fish, stingrays and seashells along the sandy floor. Dangle fish as though they were swimming above by taping them to the top of the box via thin blue thread.
On a long sheet of butcher paper, draw a line for the ocean floor about one-third of the way up the paper. Decorate the ocean floor with starfish, seashells, seaweed and coral formations. Have students draw little fish hiding in the coral and larger fish swimming overhead. Make sure the ocean floor background is sand-colored and the rest light blue to represent water.
Use crayons to color an underwater ocean scene onto thick white paper. Color heavily so that all the crayoned areas appear waxy. Paint over the picture with blue watercolor paint or very thin blue tempera. The paint will stick to the paper, but not the crayon, resulting in a lovely resist effect.