The Apkallu of Mesopotamia
Seven pre-flood sages who bring civilisation from the gods — and, in some texts, post-flood descendants of mixed parentage.
The tradition
Mesopotamian texts describe apkallu, semi-divine sages sent before the flood to give humanity crafts, writing, law and city-building. Berossus, a Babylonian priest writing in Greek in the third century BC, gives the best-known version with Oannes emerging from the sea. Later apkallu are sometimes described as of partly human descent.
The parallel
Pre-flood, semi-divine figures transmitting knowledge to humans, with a flood boundary separating eras. The structural resemblance to the Watchers story is genuine and widely noted by scholars of the ancient Near East.
The limit
Shared structure can mean shared memory, shared literary borrowing, or the same story-shape arising independently. Comparative mythology cannot by itself decide between those three.