Describe the properties of water that make it such an important molecule.
Well, without it we wouldn't exist as we do now so that is barre none the more important characteristic of water ;) Our bodies are about 70% water! That said, without further a do, some of the non-philosophical alluding properties of water that make it so important:
The most surprising thing about water is that based on what we know about the structure of atoms, water should not exist at all!
Water is less dense as a solid than as a liquid! Very few substances exhibit the same behaviour. If you've ever had a flooded basement in the winter because your pipes burst it is this property you should be cursing.
Water has an extremely high melting/boiling/critical point as a result of the hydrogen bonding. Given the mass of H20 it should have a boiling point of -90 C, but thanks to our friend hydrogen we aren't boiling out of our skins as we speak.
Water's surface has an elastic film that resists deformation when a small weight is placed on it; your paperclip can walk on water! (Ya, I know, I'm jealous too). This lets water "stick" to things like tree branches in small quantities so other than that tree still raining on you when the actual rain stops, it allows more time for plant life to absorb water.