Are you aware that water is essential for the maintenance of all life forms? Plant and animal tissue contains 70-90 per cent water. An average adult human body consists of more than 50 trillion cells (muscle, bone, skin, nerve cells just to name a few) all afloat in the "ocean" of water that composes our body.
I find water to be a wonderful substance to exhibit the character of uniqueness that is basic to the grand design because all known substances, with very few exceptions, contract their volume as liquids as their temperature decreases. As they continue to cool down they contract until they reach a temperature where they begin to crystallize, to become their solid form. Then, even as a solid, most every substance continues to shrink as the temperature drops lower and lower. Water is unique because it does not contract in this manner.
Iron contracts as it cools like nearly every other substance than water. At very hot temperatures iron is a liquid. As liquid iron cools it contracts in volume. Then at a temperature that seems very hot to us, it has cooled to a point that the liquid iron begins to become solid. Next, if we allow the iron that is now a solid to cool further it will continue to shrink in volume as it becomes more dense. This increase in density causes the solid iron to sink to the bottom of the liquid iron. And, this is exactly how nearly every substance other than water behaves. When they freeze, their solid form sinks to the bottom of their (not yet frozen) liquid form.
Water, the substance that is so essential for the existence of all life, doesn't behave in this manner. As a liquid it will contract as it cools - to a point. Then something miraculous happens. At a definite temperature of 4 degrees above the temperature that it becomes a solid it no longer continues to shrink with the drop in temperature. At that point and as it cools further to its freezing temperature water expands instead of contracting.
What is the significance of water expanding just prior to its becoming a solid? It has everything to do with the concept of context of which I spoke earlier. If we focus our attention only on the water and how the water behaves devoid of all other reference it would be similar to moving into that cut through the trees pictured above - by looking so closely we would lose the context of the surroundings. By scrutinizing water solely and by not looking how its behavior impacts other things such as life forms, that to a very large extent are composed of water, we would fail to recognize the perspective I refer to as vista.
When water expands between four and zero degrees (the temperature at which it freezes) it becomes less dense and is buoyed to the top of the warmer more dense water. Then at the surface that water, which is already very close to the freezing temperature, can more readily cool still further and begin to become a solid (freeze). That solid form of water, floats on top of its liquid form where if cooled sufficiently it will form great sheets of ice.
In the winter, when the temperatures become cold enough, the water in a pond begins to freeze. Because of its unique character water forms a crust of ice over the surface of the pond and the insulating properties of the ice diminishes the loss of further heat from the pond. As the temperature remains cold, more and more ice will form on the under edge of the ice sheet that is extended across the top of the pond, further insulating the pond from more heat loss.
To keep this example in context of how water behaves, let us suppose we had a pond of water that behaved unlike water and instead like most every other liquid. Water would freeze into a solid and those chunks would sink to the bottom of the pond. In that unnatural manner ponds would literally freeze at their bottom and more and more ice would form until the pile of ice would fill the pond from the bottom to its surface. Since water in its liquid form is such a great insulator, much of the ice formed during the winter at the bottom of the pond would not receive enough heat from the summer sun to melt it. This would result in an accumulation of more ice each winter in our ponds, lakes and oceans than would melt. Eventually these bodies of water would freeze completely solid each winter and only melt to the depth of a few feet on their surface each summer.
Now that you have a perspective that water is essential for life, what effect would there be on our planet if oceans froze solid for vast periods of time and only thawed a few feet on their surface during the summer? All animal life is sustained by the use of oxygen. The major contributor of oxygen is a microorganism in the oceans called plankton. While the oceans were frozen solid the plankton would be unable to produce oxygen. Without oxygen animal life would cease to exist.
Snowflakes, plankton and even the manner in which water freezes exemplifies diversity. The plan of the universe embraces diversity. The relationship between the various and yet individual character of all aspects are utilized in an encompassing harmony of uniqueness. All things are unique by design and possess a purpose. Surely, our human uniqueness is no less important than the water composing snow flakes.