I watched a clip of it. It did seem pretty legit up until they showed the part when a mermaid supposedly speared a fish right infront of the camera. That part was way too fake and related way too much to how they portray mermaids. I mean if mermaids really do exist and they live under water I'm pretty sure they wouldn't be using spears to catch fish, instead they would've evolved enough to be able to catch fish without using any tools just like all the other fish in the sea and no you can't compare them to humans unless Atlantis really does exist lol
The clip was used to illustrate the similarity of the using of tools between our species and theirs. Obviously it's fake, but its possible. You could say that we would've found ways to kill a lion without using tools too, if your argument was to say that mermaids (aquatic primate) do not need (er, should not need) tools.
Overall, these are theories, and thus not yet proven.
I really wanna fawk one though and cross breed to make the first "Hummaid" (this is what I'm calling it!).