it's possible that the indigenous algerian berbers had a story about their aristocracy arising from the ocean. it's a common meme in history that may have an ancient origin in the pre-neolithic danubian culture. other places it shows up in are

- the merovingian franks believed they were cimmerians. they also believed their aristocracy were fishmen that crawled out from the ocean. there is evidence of substantive western iranian migration into france in the migration period. the french name alain, and a spate of place names derived from it, is iranian in origin and the result of iranian migration into france.

- the sumerians, which probably spoke a pre-proto-indoeuropean dialect and may have origins in the black sea or danube river area, also believed their aristocracy came from the oceans.

this sumerian theory of fishman origin has been presented as a crude evolutionary theory, which is a bit of a stretch.

i have no supporting evidence, but it's possible that a similar theory was co-opted by muslim colonists in north africa and converted into a story about a syrian swimming across the sea. it's the same kind of syncretism that defines european christianity, but we've mostly figured it out through critical analysis, and they've mostly been ordered to submit and obey and not think it through. in fact, there's a convincing argument that the holy grail myth is based on a christianization of the merovingian mythology, to the idea of jesus' bloodline landing in marseilles (an ancient greek port built to export celtic goods, like salt and tin, back to greece).