Merlin and mermaids

"Tu connais les sirènes?" "Have you heard of mermaids?"
My friend Abdon, lawyer, father of thirteen children by three different wives, and a very sensible and responsible person, asks me a serious question.
"Yes, of course," I reply.
"So what do you think they are?," he asks.
I tell him that I believe they are mythical creatures, invented by lonely sailors on long voyages at sea.
Abdon laughs.
"No," he says, "they are very real."
He explains that 'mermaids' are supernatural creatures who live in the water with powers that it is best not to trifle with. I guess the look on my face is rather incredulous and skeptical, for he laughs at my ignorance.
"We all know they exist," he says.
He tells me the story of the engineer who designed and built the great bridge on the Sanaga river: "He went in the water and stayed there for several days. Only then did they start constructing the bridge. And when he died, he was buried next to the bridge."
I tell him that we have even longer bridges in the Netherlands, one even spanning an entire sea arm, and that as far as I am aware any preliminary underwater activity is to assess the state of the river bed in order to build a sturdy foundation.
"I have never heard any of our engineers say that they had to confer with mermaids before they could start constructing their bridges," I say, as if that would settle the matter.
Abdon is not convinced, however: "Of course it would be a secret, so he wouldn't be telling you, now would he?"
It is kind of hard to argue with that, but I try anyway: "But in the West we don't believe in witchcraft and magical creatures anymore. We use science, which is much more effective."
"Oh, I know that," Abdon says. "I once had this book that explained it all."
He proceeds to tell me that in this book he read that two or three hundred years ago all the sorcerers of the West were called together by their great head sorcerer ("il s'appellait Merlin" - "his name was Merlin.")
"Merlin had them all sign a pact in which they promised that from now on they would only perform 'daylight magic' that was supposed to benefit the people, instead of 'night magic', which has only negative purposes."
I don't have the heart to try and explain to him that Merlin, like mermaids, is considered a mythical creature.
Later he takes me to meet his friend, Tonton Louis. Louis is blind and has no obvious means of income, but he lives in one of the nicest houses in Obala. They tell me that is because he acts as a sort of counselor to the wealthy and powerful of Cameroon. After discussing the football World Cup for a while, Abdon tells him that I don't believe in magic.
I try to explain that my faith in science is much stronger than my faith in superstition. Like Abdon, Louis is amused.
"Science is nothing but the white man's brand of magic," he says.
I explain that whereas magic is shrouded in secrecy, science depends on openness.
"That has allowed science to progress to the point that we now have electricity and airplanes an cars."
"Ah, but magic makes progress too," Louis exclaims. "I remember that when I was young the sorcerers couldn't work their magic across a river or stream. They can now. And it is well known that when we first got electricity the sorcerer's magic couldn't penetrate houses where they had electricity. But electricity is no longer a barrier against African magic."
I still find it all very hard to believe.