Quick and easy…

Preparation:
Per student. Staple two pieces of black craft and cut out a fish shape.

In Class
Glue strips of tissue paper across one of the fish.
When done glue the second fish shape to the back.
Display on a sunny backlit window.

And with the cut out part…
Use this as part of another craft, or in a game. For example, put the fish on the floor and have them waft it across the floor with a newspaper.