Ah the legends of mermaids and not the Little one. Though Disney’s version is not the Hans Christian Anderson one.
Mermaids/Sirens have been in myths and legends for thousands of years. Are they real? Are they stories made it up as a cautioary tale for sailors?
We may never know.
But for Sylum … of course they’re real. Sparrow want’s nothing to do with them, but there is a crab fisherman who can parley with them.