'Sea monster' in the Bible

Speak, and you must say, 'thus says the Lord Yahweh: "Look! I am against you, Pharaoh, king of Egypt, the great sea monster, the [one] lying down in the midst of his Nile streams, who says to me, "[It is] my Nile, and I made [it] [for] myself."

"Son of man, raise a lament over Pharaoh, the king of Egypt, and you must say to him, '[With] a fierce, strong lion among nations you compared yourself, and you [are] like the sea monster in the seas, and you thrash about in your rivers, and you make water turbid with your feet, and you make your rivers muddy.