The Genesis mythology is probably the syncretic fragments of poems and stories gathered over time. When the Egyptians ruled the Levant, the Hebrews were pantheistic nomadic wanderers. Then they became henotheistic pastoralists and settlers under the Akkadians. During Greeks reign, they became monotheistic urban citizens. So the mythos had to keep changing.

The accreation mythos went through multiple and severe editing during the Akkadian times under the reigning Akkadian priests so as to completely remove the Hebrews from the Egyptian pantheistic influence. This became the creation myth of the OT.. Parashah B'reshit.

The Canaanites(includes the Hebrews) managed to keep some parts of the Baal cycle mythos but mostly relied on the stories from Akkadian priests.

The Akkadian Mythology itself runs parallel to the Hittite and Chaldean creation myths. Their origins are lost suggesting that there were even older creation myths from which they derived their own narrative mythology.

For example..look at Tiamat (https://en.m.wikipedia.org/wiki/Tiamat ), a salt water sea dragon/serpent who is sibling of Apsu (fresh water). Tiamat was later killed by Marduk who used her parts to create the other worlds. Marduk (storm god), the son of Enki(water god).

Genesis follows the same story structure up until the flood myth and the ark. So Hebrew creation mythos/Genesis was definitely derivative and also underwent multiple edits and rewritten over the centuries.

Ref: https://etcsl.orinst.ox.ac.uk/ : The Electronic Text Corpus of Sumerian Literature