Before Moses was born, Pharaoh had a dream. He saw a giant set of scales. On one side lay the entire weight of Egypt: the pyramids, the armies, the treasuries, the granaries, the priests, the princes. On the other side lay a single small lamb. The lamb outweighed Egypt.
Pharaoh woke unsettled. He called his magicians and astrologers and laid the dream before them. They interpreted it at once. A child was going to be born among the Hebrews, and that child would grow up to break the power of Egypt. The lamb is small, they said, but the scales do not lie.
The magicians then gave their policy recommendation. If the threat is a single Hebrew child, drown every newborn Hebrew boy at birth. They added a second prediction, which they offered as professional reassurance. They had foreseen that the redeemer's own death would one day come by water. If water was his fate, water was also his vulnerability. Water could be used against him now.
This is why Pharaoh's decree sent the newborns of Israel into the Nile. The reasoning was technical, not capricious. The magicians had the right intelligence but the wrong interpretation.
The sages note the irony. The "water" the astrologers saw was true, but the water they saw was not the Nile. It was Mei Merivah, the Waters of Strife, decades later in the wilderness, where Moses struck the rock instead of speaking to it and lost the right to enter the land (Numbers 20:13). Moses died because of water, yes, but not the water Pharaoh threw him into. The astrologers read the destination correctly and the map wrongly, and Pharaoh built a genocide on the difference (Gaster, Exempla No. 242).