About 3.6 million viewers tuned in to watch the special, which claimed to have never-before-seen footage taken of the mermaids in the Greenland Sea.
Both "Mermaids" specials were hoaxes, designed to look like real documentaries. But that didn't stop people tuning in en masse to witness a fake investigation into a mythical creature.
This is in stark contrast to Animal Planet's usual fare, which includes such reality based programming as "Meerkat Manor" and the "Puppy Bowl."
In a statement, Animal Planet's president and general manager Marjorie Kaplan said, "The phenomenon of 'Mermaids' has truly been a watershed -- and a watercooler -- moment for Animal Planet. These extraordinary television specials have electrified, challenged and entertained television audiences and online fans alike."
Many people on Twitter seemed to believe that mermaids could exist, despite the lack of real evidence.
In writing about the special, Times writer Ed Stockly noted, "It's remarkable how well this fake documentary mimics actual programs claiming to reveal actual creatures. Substitute Mermaids for Bigfoot,
"While this production won't fool many skeptics (at least I hope not), I can only imagine that the same audiences that lap up shows about Bigfoot, ghosts, psychics, etc. will miss the disclaimers and buy into this one too. Mermaids could be the new Nessy."