When the Israelites arrived at a place called Marah they were thirsty, but the water there was "bitter" so they could not drink it. What did they do? Complained. God heard them and when Moses threw a piece of wood into the water, it became sweet and they could drink it. Isn't that weird? What was that all about? Eventually the people came to Elim where they found twelve springs of fresh water, one for each of the twelve tribes of Israel. It is quite a story!