Before the fourth plague, God sends Moses back to the water. Targum Pseudo-Jonathan on Exodus 8:16 restages the old dawn scene: Arise in the morning, and stand before Pharoh: behold, he goeth forth to observe divinations at the water, as a magician.
Nothing has changed in Pharaoh's morning routine. Three plagues in, the king of Egypt is still walking down to the Nile at sunrise to read omens from its surface. The plagues have not cured his idolatry; they have deepened his anxiety. A confident ruler does not need to check the water every day.
The meturgeman's repetition of as a magician is devastating. Pharaoh, the man Egypt treats as a god, is exposed again as a practitioner — someone desperately reading the river for comfort. And Moses is to meet him there, at the exact spot of his spiritual weakness, with a fresh demand: Emancipate My people, that they may worship before Me.
Note the verb. Pharaoh is divining; Israel is being asked to worship. The contrast is the entire theological argument of the Exodus. Divination extracts forecasts from a river. Worship gives thanks to the Maker of the river. One is fear dressed as religion; the other is relationship dressed as service.
The takeaway: you can identify a false god by how nervous its worshippers look at sunrise.