Life begins and depends on the strange physical and chemical properties of water. This lecture by Denis Noble was delivered to a Biology Congress in Iran in 2022. In simple language it shows why water is crucial to our ability to exercise free action in choosing our actions and in being creative. The lecture ends with a plea: water resources in many part of the world are threatened by global warming, while in other parts of the world people and animals are threatened by massive flooding. Recognising how important water is to life, and why that is so, is a major step towards convincing people and nations around the world to take action to prevent the catastrophes that threaten life on earth.