Science Experiments Density

Question: what is water? science help?
Science experiment: you will be given two substances, water and something very similar but not exactly the same as water. aside from boiling, density, freezing, suds, touch,ph, evaporation, tests etc. come up with your own EXTREMELY CREATIVE test as to which one is water. ingesting is not an option, you will be graded on creativity.
ANY IDEAS?
Answer: H20
The Quirkles KOLR 10 Density Dan Science Experiment