Thus says Yahweh, "By this you will know that I [am] Yahweh. Look, I [am about to] strike with the staff that is in my hand the water that is in the Nile, and it will be changed to blood. And the fish that [are] in the Nile will die, and the Nile will stink, and [the] Egyptians will be unable to drink water from the Nile." '" And Yahweh said to Moses, "Say to Aaron, 'Take your staff and stretch your hand out over the waters of Egypt and over their rivers, over their canals, and over their pools and over all of their reservoirs of water, so that they become blood,' and blood will be in all the land of Egypt and in [vessels of] wood and of stone." read more.
And Moses and Aaron did so, as Yahweh had commanded, and he raised the staff and struck the water that was in the Nile before the eyes of Pharaoh and before the eyes of his servants, and all of the water that was in the Nile was changed to blood. And the fish that [were] in the Nile died, and the Nile stank, and [the] Egyptians were not able to drink water from the Nile, and the blood was in all the land of Egypt. And the magicians of Egypt did likewise with their secret arts, and Pharaoh's heart was hard, and he did not listen to them, as Yahweh had spoken. And Pharaoh turned and went to his house, and {he did not take also this to heart}. And all of [the] Egyptians dug around the Nile [for] water to drink, because they were unable to drink from the water of the Nile. And seven days passed after Yahweh struck the Nile.

when he turned their rivers to blood so they could not drink [from] their streams. Verse ConceptsBlood, as symbol of guiltTurned To Blood

He turned their waters into blood and it killed their fish. Verse ConceptsBlood, as symbol of guiltTurned To BloodDeath Of Creatures