Always be respectful, do not be abrupt or intrusive, and the most important... Introduce yourself and tell them why you are there.
Believe it or not, ice is actually about 9% less dense than water. Since the water is heavier, it displaces the lighter ice, causing the ice to float to the top. How is ice less dense than water? ... So for water, the density actually decreases along with a decrease in temperature - causing ice to be less dense than water!
I believe that substance would be water.
