small box (shoe boxes work really well) paper and cardboard string glue scissors tape paints, glitter, pencils Paint the inside of the box a watery blue and give it a glittery floor. While the water dries, get cracking on the miniature props and characters. Draw seaweed on a piece of green cardboard. When you cut it out you will need to leave a tab on the bottom so you can stick it onto the diorama floor. make some coral the same way or even from doily. Starfish? Rocks? go ahead!