Here the Targumist drops a myth into the middle of the verse. Targum Pseudo-Jonathan on (Genesis 1:21) says the Lord created the great tanninim — sea dragons — and among them Leviathan and "his yoke-fellow," his mate. And the Targum tells us something the Torah does not: they "are prepared for the day of consolation."
In Jewish tradition, Leviathan will be the banquet served at the end of days, at the feast for the righteous in the messianic age. The Talmud (Bava Batra 74b-75a) describes it at length: God slew the female leviathan at creation, salting her flesh for the coming world, because if the two had reproduced, the earth could not contain them.
The Targumist plants the seed here. On the fifth day, deep in the swarming of ocean life, creation is already pointing forward to its own consummation. The wild sea beasts are not just zoology — they are eschatology. The righteous will one day sit and eat of what was made before any human foot touched the ground.
The verse closes with a quiet detail the Targum adds: the waters brought forth creatures "clean and unclean." Before Sinai, before the laws of kashrut, the categories are already present in the bones of creation.