Other Density Demos:
Use a triple beam balance of electronic scale to teach or practice that skill
Use hot and cold water instead.
Compare salt and fresh water and connect with the environment.
Have older students teach this to younger students.
Use other liquids to make density columns. (Water, oil, alcohol, etc.)
Make a much larger one as part of a science night.
Let students try making different density salt solutions and try to figure out which ones work the best and how that relates to density.
Egg in salt water or tap water
Ice in water or rubbing alcohol
I attached a Word document that is a template for a guided lab report that you feel free to modify and use.
Other Ideas and Resources:
These are just some ideas and alternate extensions.
Some additional references will many different versions of this same idea:
DENSITY: SALTWATER COLUMN LAB TEACHER PREPARATION
Explains a different way to prepare solutions and some "discussion" questions as a worksheet for students
Written from the standpoint of ocean science for elementary school. Contains a lot of "teacher lingo" (e.g. key concepts, big idea, objectives, etc.)
GEMS: Discovering Density book
This book costs $18, but I think is where I first saw the idea for this lab. The handouts are free online in Spanish. So that might make this a cool activity to do with students learning Spanish too!
Steve Spangler 7-Layer Density Column
This link provides a video showing a different density experiment with different types of liquids to see how their relative densities are different. They do use the word "heavier" instead of density. He uses a slightly different way of layering.
NOAA Lesson Plan: Hot, Cold, Fresh and Salty
Another Earth Science/Oceans connection. This lesson plan gives ideas about having students compare hot and cold water and fresh and salty water. These are extensions that would be great to add to a simpler lesson like the one I posted.