It reeled in the network’s biggest audience in its 17-year history and caused an immediate Twitter frenzy that is still trending today.

But Animal Planet’s Sunday ‘documentary’ about the existence of mermaids was nothing but a hoax, it emerged today, a revelation that will likely disappoint the show’s record 3.6 million viewers.

‘Mermaids: The New Evidence’ was advertised as a follow-up to last year’s ‘Mermaids: The Body Found’, with biologist Dr Paul Robertson returning with what appeared to be brand new footage of the alleged mythical creatures, allegedly taken this spring in the Greenland Sea.

Such was its popularity that it drove the network to the number one slot in the key demographic among 25-to-54-year-olds and after it was broadcast, 1.5million streams of mermaid-related video surfaced online.

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Popular: Animal Planet’s ‘documentary’ about the existence of mermaids drew the network’s largest ever audience of 3.6million viewers

Specialist: Biologist Dr Paul Robertson returned with what appeared to be brand new footage of the alleged mythical creatures, allegedly taken this spring in the Greenland Sea

But those millions of viewers seem to have missed the blink-and-you’ll-miss-it disclaimer at the end which described the program as ‘science fiction’ based on ‘scientific theory’.

The special ‘documentary’ showed video of a supposed mermaid sighting and featured an exclusive interview with a man they claimed was a former scientist with the National Oceanic and Atmospheric Administration (NOAA).

But the ‘scientist’ was actually an actor and the ‘mermaid’ in the footage was fake.

The program even suggested a government cover-up of mermaid evidence, complete with a spin-off site that said it has been seized by the U.S. Department of Justice and the Department of Homeland Security.

Hoax?: As the creature swims away from the vessel, an alien-like face can be seen swimming away, which prompted online rumors of the existence of mermaids

Twitter erupted with posts about the show and the existence of mermaids in the hours and days that followed.

‘Sabrina’ posted ‘Both documentaries, Mermaids: The Body Found and Mermaids: The New Evidence have sufficient proof.’

‘White storm’ tweeted: #NW Mermaids: The New Evidence. Go ahead and tell me mermaids aren’t real after watching that special,’ while ‘g-host’ wrote: ‘Did y’all see MERMAIDS the new evidence???? there are mermaids out there for sure….!!!!!’

The show’s executive producer Charlie Foley said they wanted people to think it was real and made it into a documentary-style program.

He told ABC News: ‘We wanted people to approach the story with a sense of possibility and a sense of wonder. Hopefully that’s what Mermaids allowed viewers to do…allowed them to suspend their disbelief.’

NOAA’s put out a statement on it website saying: ‘Mermaids: The New Evidence is just entertainment. No evidence of aquatic humanoids has ever been found.’

Due to its popularity, the network is thinking of making another mermaid-based show. Animal Planet’s previous all-time record holder was ‘Dragons: A Fantasy Made Real’.