On Wednesday, Disney announced that Halle Bailey of Chloe x Halle will be playing the starring role of Ariel in the upcoming live-action remake of animated movie, The Little Mermaid.

It seems like good casting. With a lot of singing required, who better than a Grammy-nominated singer in the right age range to play the lead?

Of course, some aren't happy about this casting. In fact, people have spent the past two days on social media throwing a tantrum because the newest portrayal of an imaginary creature in cartoon form isn't quite white enough for their tastes. 

They're so mad that some of them have now started to try and use "science" to prove that if a half-woman half-fish creature did exist they would be white. 

"Mermaids live in ocean. Underwater = limited sunlight. Limited sunlight = less melanin. Less melanin = lighter skin color," one tweeted. "Because they live underwater, which has no access to light beyond a certain depth, Ariel and every other mermaid in existence would be albino."

"Correct me if I'm wrong," another wrote. "But isn't it physically impossible for Ariel to be black? She lives underwater, how would the sun get to her for her to produce melanin?! Nobody thought this through..?"

Let's leave aside that they are attempting to apply "science" to a story about a mythical fish child of King Triton doing battle with a sea witch with octopus legs, with some help from a singing crab with a dubious Jamaican accent. Let's also leave aside that there are already non-white mermaids in Disney's Little Mermaid canon.

Not all sea creatures are white. Rainbow fish are not white. Orcas are not (all) white. Even white fish are mostly black, brown, and green. 

Manatees, the animals it's generally accepted mermaid myths were based on, are also not white, they're a sort of brownish-gray, and apparently not very attractive. In 1493, Christopher Columbus, sailing near the Dominican Republic, saw three and wrote that mermaids are “not half as beautiful as they are painted."

As for the idea a mermaid couldn't make melanin, many species of whale avoid Sun damage from UV radiation thanks to high levels of melanin pigments in their skin, just like humans.

"Applying science to mermaids is a rather silly thing to do, they are symbols not biological creatures. Also, the science I have seen being used is really bad science: Cherry-picking elements of the natural world to argue why Ariel should be pale and redheaded makes no sense," Sacha Coward, mermaid folklorist and freelance museum professional told IFLScience.

"In these cases 'science' is being used as a proxy to back up racism. White people feeling a sense of ownership of a symbol from their childhood are trying to use wacky arguments to 'keep Ariel white'."

"But, just for the hell of it: Ariel lives in a warm coral reef, the biota around her implies she is not of European descent," Coward continues. "White skin and bright red hair would also be a dead giveaway to predators. With that in mind, looking at other aquatic mammals, Ariel is comparatively malnourished. A real mermaid would probably be a large tan-skinned creature with plenty of blubber, hairless and sleek with paddle-like flippers!"

"You see, bad science can be used to argue any point you wish to make," he added. "I've just made the case for Ariel to be cast as a manatee."

As well as dodgy science, some people argued that the casting of a black actor went against traditional folklore. However, as Sacha points out in this excellent Twitter thread, mermaid folklore has long existed around the world, and like all folklore, is a mirror held up to each society, hence the portrayal of these mythical creatures with a variety of skin colors, fish parts, and powers long before she was a singing white redhead in 1989.