Exodus 7:20-21

So Moses and Aaron did even as the LORD had commanded. And he lifted up the staff and struck the water that was in the Nile, in the sight of Pharaoh and in the sight of his servants, and all the water that was in the Nile was turned to blood. The fish that were in the Nile died, and the Nile became foul, so that the Egyptians could not drink water from the Nile. And the blood was through all the land of Egypt.