Eisler saw fish symbolism everywhere and assumed a connection between Christianity and pagan fish cults. He also claimed that Jesus’ statement that the Baptist came “eating no bread and drinking no wine” (Luke 7:33) shows dependence on Berossus’ statement that Oannes “took no food” during daylight hours when he was above sea level. Eisler elides both of these statements to make them say that neither figure ever “ate nor drank,” though this is clearly not the meaning of either. (John eats locusts and honey as per Mark 1:6.) Eisler also leaves out the fact that abstaining from certain earthly food or drink is a mark of holiness in the Bible. John the Baptist is forbidden wine by divine decree because it was forbidden to all Nazarites, a mark of special holiness (Luke 1:15 with Numbers 6:3). But also: God forbids fermented liquids in the Tent of Meeting (Leviticus 10:9). Similarly, while in the presence of God on Sinai, Moses “ate no food and drank no water” (Deuteronomy 9:9), just as Saul abstained from food and drink in the presence of Jesus on the road to Damascus (Acts 9:9). Are all they Oannes, too?
By contrast, Oannes partook of no human food because he was not a human any longer. But to understand this means exploding one more misconception. Eisler and de Santillana and von Dechend assume wrongly that Oannes is a corruption of “Ea-Hani,” making Oannes an avatar of the water god Ea (the Sumerian Enki). This was somewhat possible to support when all that was known of him was Berossus, but in light of the cuneiform inscriptions of Nineveh and Tel-al-Amarna, it is insupportable. These inscriptions confirm that Oannes is a Greek transliteration of Uan, an alternate name for Adapa. Adapa is one of the Seven Sages, who was offered the food of the gods but, on bad advice, declined it, losing immortality. When Berossus says Oannes ate no human food, he is referencing a somewhat corrupt tradition about Adapa and the gods’ food. (Or, more likely, the Greek summarizers misunderstood whatever Berossus really said—as evidenced from discrepancies between the Greek summaries of Berossus and the Enuma Elish.)
Now, as a point toward the Baptist comparison, it is true that John the Baptist was called a fisher of men in southern Mesopotamia, and Adapa was known as he who “fish[ed] for his [Ea’s] temple at Eridu.” Adapa was believed to have been banished by the gods to the underground sea for hubris, but to have returned from time to time to teach wisdom. In this, he may well have been seen in late Antiquity as an analogue to John the Baptist, must the way the similarity in name and iconography between Elijah and Helios led to the saint with the fiery chariot taking over for the god with his fiery chariot in many local cults.
But Eisler is wrong to claim Berossus knows six reincarnations of Oannes. He seems here to be referencing Berossus’ statement that several beings like Oannes rose from the sea “after him.” These would be the Seven Sages, I suppose, though elsewhere he calls them seven of the first ten kings of Babylon. There is no indication that they are reincarnations, or that their lives were successive rather than overlapping.
De Santillana and von Dechend see in Eisler’s mistakes the prototype of the Sleeping King. They follow him in mistaking Oannes for Ea, and identify Ea with the planet Saturn, which they then identify with the god Kronos (the Roman Saturn). However, Ea was not associated with the planet Saturn but with Mercury, according to the Sumerian tablets (though this was not consistent through time). Ea in the Enuma Elish Ea casts a spell on the god Abzu to put him to sleep, but this is hardly the same as being the sleeping god himself.
By contrast, the Sleeping King story is very much an Indo-European story, found from the Celtic fringe straight through Europe to Greece. (A very few, very late stories from the Americas use the same motif, but these are post-Conquest in origin and derive from European sources.) There are dozens upon dozens of these sleeping gods/kings in their mountains, of whom Charlemagne and Frederick Barbarossa are among the latest. De Santillana and von Dechend discuss Plutarch’s report of Kronos’ imprisonment on Ogygia and ask us to read it as cosmology, but it is just another variation on the Sleeping King motif. The fact that Plutarch’s longer discussion of the myth in the Moralia (De Faciae 27) is very much a morality tale about what makes one Greek does not inspire confidence that it hides a cosmological core. The shorter of the two discussions (De Defectu Oraculorum 18), is attributed to British holy men—Celts, possibly Druids—and suggests that a separate Celtic version was then in existence and that some syncretism between Celtic and Graeco-Roman versions had already occurred by Plutarch’s day.
If this is true, then Plutarch’s use of the planet Saturn is a Greco-Roman layering onto the myth of Hellenistic astrology (which, incidentally, did know of precession), not necessarily an original characteristic—especially since it isn’t found in any other Indo-European version of the story, and, no, not even in the unrelated story of Oannes.