Well, I posted a couple threads on this forum on the topic in case you were unaware of the subject. Leolaia was certainly not the end of any discussion, in fact we disagreed on many finer points. I would also imagine she would have sharpened her understanding over the last 20 years (as I have) as well. To anyone interested in this topic, however, her reviews were a great resource from which to pursue further research.
On this topic, while I find Tsumura’s primary arguments sound, his conclusions/objections are something of red herrings. He seems to believe he is making observations others are unaware of. While some, especially early in the history of comparative religion research, may have suggested the authors retained the chaos theology, recent scholarship points out the language reflects a cultural linkage/indebtedness. Especially considering the lateness of the hexaemeron (5th-3rd) we would not expect the author to be simply repeating creation stories from a thousand years previous. He rather demonstrates the persistence of an ancient motif. Much like today when we refer to 'forbidden fruit' or making someone a 'scapegoat', these are metaphors/idioms/motifs that carry meaning separate from the larger specific religious origins. Cross used to say, when the language no longer posed a threat to the scribal elites, they were adopted and transformed in subtle ways. However, it's not just the words it's also some underlying conceptual theme that persists. In other words, my audience knows what being a 'scapegoat' is even if most have no idea where it came from nor are religiously Jewish.
In the case of the dividing waters, the idiom is also utilized in fresh ways by the second temple author/redactors. It would seem in many contexts the symbolism is no longer narrowly related to 'creation' but fresh beginnings and demonstrations of divine power. Note in the exodus stories the similar elements of tehom/yam interacting with wind/breath from God parting the sea as a divine act opening a new chapter for Israel. Perhaps the author intended a back reference to Gen 1 (as I suggested), perhaps not consciously. Regardless the idiom and motif are present.
So, I'm convinced the shaping of a formless world into a habitable world, and of dividing waters as are clear examples of inherited metaphor that was recognized by nearly anyone in the ANE.
As I said in my first post it's a hobby for me, hobbies should be fun. I don't feel like we're having fun any longer, so I'll let you go. Good luck with your research.