In this demonstration, Sulphur Hexafluoride which is denser than air is poured onto a fish tank. Since it is denser than air, it accumulates in the bottom of the container and a buoyant force acts to keep the aluminum boat afloat in this sea of Sulphur Hexafluoride.
You can use the principles that you have learned in the last few sections to tackle this problem as well.
The only difference is that 
Questions to ponder:
- People float on the dead sea because the density of sea water is greater than the average human density. If you consider a sea of Sulphur Hexafluoride, what are the conditions under which a human could possibly float on it?
Source for the Sulphur Hexafluoride demonstration – https://www.youtube.com/watch?v=1PJTq2xQiQ0
9b-Discussion notes 