I also thought that this observer we speak about, must have been immersed in a cultural context, obviously influenced by the myths, legends and gods of his culture and of course, exposed to other creation narratives.
If the location we propose is correct, he must have had great influences of Babylon. Knowing then what the Babylonians said in his texts on this event can be very interesting.
I transcribe below the Babylonian poem of creation called Enuma Elish (for its first two words) which begins:
When the sky above had no name,
And the very earth beneath was not yet named,
(Then) the waters of the primordial abyss (APSU: freshwater)
and of the tumultuous Tiamat (salt water) were mingled together.
This poem Enuma Elish, found in the library of Ashurbanipal in Nineveh (669 BC - 627 BC), records the birth of Marduk, his heroic deeds and how he became the lord of the gods after killing his grandmother, Tiamat, from whom he snatched the Tablets of Destiny.
"When high above heaven had not been named it had not been called with a name the mainland below; and there was just the primordial Apsu, their father, (and) Mummu-Tiamat, she who bore them all, mingled their waters as one body.
And no field was formed, no marsh was to be seen, when none of the gods existed, and none bore a name, and no destinies were ordained; then Lahmu and Lahamu were called into being. During eternities they increased in age and height. Anshar and Kishar were formed, surpassing the others. Days passed, years accumulated. Anu was his son, a rival of his own parents, yes, Anu, Anshar´s firstborn, was his equal. Anu begat Nudimmud in her own image. Nudimmud became their parents' owner, unparalleled wise, insightful, strong and powerful, much stronger than his grandfather Anshar.
He had no rival among the gods his brothers. Together the divine brothers came and went altering Tiamat when they shook from side to side; yeah, they altered Tiamat with their hilarity in their heavenly abode...