Then Moses had Israel leave the Reed Sea and go out into the Shur desert. They traveled for three days in the desert and found no water.
References for Exodus 15:22
When they came to Marah, they couldn't drink Marah's water because it was bitter. That's why it was called Marah.
References for Exodus 15:23
The people complained against Moses, "What will we drink?"
Moses cried out to the LORD, and the LORD pointed out a tree to him. He threw it into the water, and the water became sweet. The LORD made a regulation and a ruling there, and there he tested them.
The LORD said, "If you are careful to obey the LORD your God, do what God thinks is right, pay attention to his commandments, and keep all of his regulations, then I won't bring on you any of the diseases that I brought on the Egyptians. I am the LORD who heals you."
Then they came to Elim, where there were twelve springs of water and seventy palm trees. They camped there by the water.