The gods, as they (the Greeks) say, did not exist from the beginning, but each of them was born just as we are born. And this is agreed by them all, Homer saying
Oceanus the genesis of the gods, and mother Tethys
(Il. 14.201), and Orpheus -- who was the original inventor of the gods’ names and recounted their births and said what they have all done, and who enjoys some credit among them as a true theologian, and is generally followed by Homer, above all about the gods -- also making their first genesis from water:
Oceanus, who is the genesis of them all.
For water was according to him the origin of everything, and from the water mud formed, and from the pair of them a living creature was generated, a serpent with an extra head growing upon it of a lion, (and another of a bull,) and in the middle of them a god’s countenance; its name was Heracles and Time. This Heracles generated a huge egg, which, being filled full, by the force of its engenderer was broken in two from friction. Its crown became the heaven, and what had sunk downwards, earth. There also came forth an incorporeal god.