God created the great sea monsters, and all the living creatures of every kind that creep, which the waters brought forth in swarms, and all the winged birds of every kind. And God saw that this was good.

The Sages taught: There was an incident involving Rabbi Eliezer and Rabbi Yehoshua, who were traveling on a ship, and Rabbi Eliezer was sleeping and Rabbi Yehoshua was awake. Rabbi Yehoshua trembled, and Rabbi Eliezer awoke. Rabbi Eliezer said to him: What is this, Yehoshua; for what reason did you tremble? Rabbi Yehoshua said to him: I saw a great light in the sea. Rabbi Eliezer said to him: Perhaps you saw the eyes of the leviathan, as it is written: “And his eyes are like the eyelids of the morning” (Job 41:10)...

The verse states: “And God created the great sea monsters” (Genesis 1:21). Here, in Babylonia, they interpreted this as a reference to the sea oryx. Rabbi Yoḥanan says: This is leviathan the slant serpent, and leviathan the tortuous serpent, as it is stated: “In that day the Lord with His sore and great and strong sword will punish leviathan the slant serpent, and leviathan the tortuous serpent” (Isaiah 27:1).

התנינים THE HUGE CREATURES — the large fishes that are in the sea; and according to the statement of the Agada (Bava Batra 74b) it means here the Leviathan and its consort which He created male and female. He, however, killed the female and preserved it in salt for the benefit of the righteous in the time to come, for had they been permitted to be fruitful and to multiply the world could not have endured because of them.

(6) You made the deep cover it as a garment; the waters stood above the mountains. (7) They fled at Your blast, rushed away at the sound of Your thunder—(8) mountains rising, valleys sinking—to the place You established for them. (9)You set bounds they must not pass so that they never again cover the earth.

8)Who closed the sea behind doors, When it gushed forth out of the womb, (9) When I clothed it in clouds, Swaddled it in dense clouds, (10)When I made breakers My limit for it, And set up its bar and doors, (11) And said, “You may come so far and no farther; Here your surging waves will stop”?

And in the great sea monsters, God made a change in their creation - as we have said - and He didn't state in [a more] general [fashion], "And He created the souls of the sea monsters and all the souls, etc.;" by which the verse revealed that they are different from everything [else] in the waters; since besides that God implanted a soul within them, also in the power of their creation itself, God created an extra power within them; since there is no power within the waters to make it, as we have said. And this is the amazing fish, it is the leviathan, and its matters are explained in [the] words of [the Sages], of blessed memory (Bava Batra 74b). And the reason it did not state about this creation, "and it was so," is that there is no place for it, since it is not needed to say "and it was so" except when only the proclamation of God is stated; [there] the Torah tells "and it was so," since He [had] said, "let there be;" which is not the case when it states, "And He created" - proclamation is included in it, execution is included in it.