וַיִּבְרָ֣א אֱלֹהִ֔ים אֶת־הַתַּנִּינִ֖ם הַגְּדֹלִ֑ים וְאֵ֣ת כָּל־נֶ֣פֶשׁ הַֽחַיָּ֣ה ׀ הָֽרֹמֶ֡שֶׂת אֲשֶׁר֩ שָׁרְצ֨וּ הַמַּ֜יִם לְמִֽינֵהֶ֗ם וְאֵ֨ת כָּל־ע֤וֹף כָּנָף֙ לְמִינֵ֔הוּ וַיַּ֥רְא אֱלֹהִ֖ים כִּי־טֽוֹב׃
上帝創造了海中的巨大魚類，以及各種游動的活物，就是水中大量滋生的，各從其類；又創造了各種有翅膀的飛鳥，各從其類。上帝看這是好的。
Rashi
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.
Ibn Ezra
"that crawls" - meaning, "goes", and there are those who way that the [letter] shin is in place of the [letter] samech, and there are those who say
Ramban
AND G-D CREATED THE GREAT SEA-MONSTERS. Because of the great size of these creatures, some consisting of many Persian miles — the Greeks in their books even relate that they knew some of them to be 500 Persian miles long, and our Rabbi likewise spoke of them in magnifying terms187Baba Bathra 73b. — on account of that, Scripture explicitly ascribes their creation to G-d for He brought them forth from nought from the beginning, as I have explained the expression b’riyah (creation). Similarly, Scripture does so in the case of man188Verse 27: And G-d created man in His own image. on account of his exaltedness, thus informing us that man, with his mind and reason, also came forth from nought.
I wonder why it does not say “and it was so” on this day? Perhaps it would not have been possible to mention And He created after saying, “and it was so,” since it refers to the preceding.189If Verse 20 (Let the waters swarm with swarms of living creatures, etc.) would have concluded with the expression and it was so, it would have implied the creation of the sea-monster, since they also swarm in the waters. How then could it say in the following verse, And G-d created the sea-monster, as if it were another act of creation? To say, and it was so after vayibra (And He created) is also not possible for this would be redundant. Hence on the fifth day, the expression and it was so does not appear in Scripture.
Our Rabbis have said190Baba Bathra 74b. that the great sea-monsters are the Leviathan and its mate which He created male and female. He then slew the female and preserved it in salt for the benefit of the righteous in the hereafter. It is possible that on account of this it would not have been appropriate to say concerning their creation, “and it was so,” since they did not continue to exist [in the form in which they were created].
I wonder why it does not say “and it was so” on this day? Perhaps it would not have been possible to mention And He created after saying, “and it was so,” since it refers to the preceding.189If Verse 20 (Let the waters swarm with swarms of living creatures, etc.) would have concluded with the expression and it was so, it would have implied the creation of the sea-monster, since they also swarm in the waters. How then could it say in the following verse, And G-d created the sea-monster, as if it were another act of creation? To say, and it was so after vayibra (And He created) is also not possible for this would be redundant. Hence on the fifth day, the expression and it was so does not appear in Scripture.
Our Rabbis have said190Baba Bathra 74b. that the great sea-monsters are the Leviathan and its mate which He created male and female. He then slew the female and preserved it in salt for the benefit of the righteous in the hereafter. It is possible that on account of this it would not have been appropriate to say concerning their creation, “and it was so,” since they did not continue to exist [in the form in which they were created].