This DIY experiment teaches students about solubility and density.  We’re going to have floating fish for this one but you can draw anything you like, just make sure all the lines are connected.

What you need + steps

• Dry-erase or whiteboard marker
• Solid colour plate or shallow glass bowl (flat bottom is better for drawing)
• Measuring cup with spout – filled with water

1. Draw the outline of a fish on the bottom of the crockery plate or dish using your whiteboard/dry-erase marker. Retrace your drawing to make sure all the lines are connected. Let it dry for a minute or two.
2. Fill the cup with tap water. Place the pour spout just inside the corner of the dish and add water very slowly until it just covers the bottom of the plate. Be careful not to pour water directly onto your drawing or make splashes near it. The water will move toward your drawing, eventually surrounding it. Observe what happens. If the water splashes or it doesn’t work on your first try, empty the dish, erase the drawing with a paper towel, dry off the dish, and try again.
3. Slightly tilt the dish slowly from side to side.

What happens?

The ink in whiteboard markers is engineered to be slippery. It’s made with a chemical that causes it to easily release from surfaces. (Permanent markers are made with a chemical that makes the ink stick to surfaces, so be sure not to use these in your experiment!)

The easy-release ink lets go from a surface, but why does it float? There are two reasons. First, whiteboard marker ink isn’t soluble, which means it won’t dissolve in water. Second, whiteboard marker ink is less dense than the water, so it becomes buoyant, meaning it can float. When you tilt the dish, your picture moves around on the water’s surface.

Source:  https://www.goodhousekeeping.com/life/parenting/g32176446/science-experiments-for-kids/