The Pharaoh of Ezek. chap. 32 was another tyrant ruler / king who was oppressing the people, and was compared to a lumbering predator animal who when entering the waters stirs up the dirt, and turns the clear flowing water into muddy streams.
Ezek. 32:2, (YLT)
"`Son of man, lift up a lamentation for Pharaoh king of Egypt, and thou hast said unto him: A young lion of nations thou hast been like, And thou [art] as a dragon in the seas, And thou comest forth with thy flowings, And dost trouble the waters with thy feet, And thou dost foul their flowings."
Throughout all of the scriptures beasts of prey were used to indicate tyrants and oppressive rulers and nations. They were beasts because they fed off the people. Today we call them parasites.
In the OT, it is the serpent in Ex. 7:9-10; the representation of Nebuchadnezzar as a dragon in Jer. 51:34; the representation of the idolatrous tribes of Israel in Deu. 32:33; the representation of Babylon in Isa. 27:1; 51:9; and the representation of Pharaoh, king of Egypt in Ez. 29:3.
The symbolic use of “dragons” and “serpents” meant the pagan, heathen nations who worshipped and sacrificed to idols, the unclean things they made with their own hands. Those pagan, idolatrous nations were always the enemies of the Most High.
We may not have specific knowledge of the evil deeds this Pharaoh performed, but generally he followed after his kind in stealing, extortion, murders, lies, etc.
Clarke likened the animal in the waters to a crocodile which is common to the Nile. But, the Holy Spirit's use of the serpent/ dragon imagery is consistent for all evil tyrants who used their position of power against the people.
"The prophet goes on to predict the fall of the king of Egypt, under the figure of an animal of prey, such as a lion or crocodile, caught, slain, and his carcass left a prey to the fowls and wild beasts, Ezekiel 32:1-6. The figure is then changed; and the greatness of his fall (described by the darkening of the sun, moon, and stars) strikes terror into all the surrounding nations, Ezekiel 32:7-10. The prophet adds, that the overthrow of the then reigning Egyptian dynasty was to be effected by the instrumentality of the king of Babylon, who should leave Egypt so desolate, that its waters, (alluding to the metaphor used in the second verse), should run as pure and smooth as oil, without the foot of man or the hoof of a beast to disturb them, Ezekiel 32:11-16." Source: here
The rest of Clarke's commentary on Ezek. c. 32 is worth while. I also enjoy the article on the "Demise of Pharaoh" at ProphesyProof.
Secular history reports that Nebuchadnezzar defeated Pharaoh Necho II at the battle of Carchemish in 605 BC. (See here and here)
It is interesting that a prominent note in all of the histories I find for Pharaoh Necho II is that he envisioned and began a project to build a canal between the Nile and the Red Sea.
Muddying the waters?