Water is one of the most amazing substances on earth. It contradicts almost all of the rules of physics and chemistry. For instance, it has the unique characteristic of expanding and growing lighter when it becomes solid. All other substances grow heavier upon turning solid and contract as the temperature decreases. This is what causes ice to float on top of water, instead of collecting on the bottom, which makes all the difference for aquatic life and in fact for all life on earth. In addition, water has the highest specific heat of any substance, which makes it a superb heat reservoir and heat equaliser. Without water, the earth would be a desert because of fluctuations in heat.