No. There is no evidence of the existence of merpeople.
It isn't currently known whether ANY alien creatures even exist.
It is physically impossible to turn yourself into a mermaid. Mermaids and merpeople in general do not exist. They are the stuff of fairy tales.
Mermaid people
Merpeople, also known as mermaids or mermen, are mythical creatures that exist in folklore and mythology. While there have been accounts and mythical stories about mermaids throughout history, there is no scientific evidence to support their existence in the real world. Merpeople remain creatures of imagination and fantasy.
That is the correct spelling for the imaginary beings "merpeople" (mermaids and mermen). The English term is merfolk. If you wanted to keep the Latin mer with a latin root it would be mergens.
merpeople
Whatever you want them to look like, considering that they are fantasy creatures.
No. Merpeople do not exist and never did. Atlantis, if it existed at all, was probably destroyed by a tsunami of possibly a caldera-forming volcanic eruption. If this is the case, those who did not escape the disaster would simply have died.
merman is a boy, mermaid is a girl, and all together they are called merpeople.
The King of the Merpeople -- Ariel's father -- is King Triton.
There is no such thing as merpeople.
Merpeople and the Giant Squid. Hope I could help! :)