In order to survive humans need water, food and shelter. These three basic elements provide a foundation for humans to sustain life. The earth is composed of 70% water and more than half human body consists of water. Without clean water to drink, a person cannot live longer than a couple of days. Additionally, a person can only live for a couple of weeks without food and shelter. Therefore, it important for children to understand that in order to be healthy, it is necessary to eat a nutritional diet and drink water. This lesson is also good if you would like to incorporate a gardening aspect to your program.