Question

Looking at the data from both pages, what must be true about the density of
an object in order for it to float?

Answer 1

http://phet.colorado.edu/sims/density-and-buoyancy/density_en.html

Answer 2

Cool animation! What do you see when playing with it by picking different materials? As you can picture from imagining objects that you've seen in water, more dense objects sink.

Or is there another aspect of the animation that you have questions on?