Fill a clear bottle or jar about one-third full with water
Add vegetable oil until the container is nearly full, leaving some space at the top
Add several drops of food coloring
Break an effervescent tablet into small pieces
Drop one piece into the bottle
Watch the colored bubbles rise and fall
Add more tablet pieces as needed to keep the effect going
Seal the container only if you are not using it again soon
Place the bottle on a stable surface during use