If you like to decorate for your units, this is a great time of year to pick up the Gemmy Lightshow Lights. Our local Lowes and Big Lots stores both have them.
We use the blue ones to create water effects and the red ones to create flame effects.
Attached is a picture of our "furnace" figures that we created with plastic tablecloths and cellophane for our Daniel and his Three Friends Unit.
We are also using the blue inside our whale/big fish that we are currently using for Jonah.