Mermaid Snow

Mermaid Snow is the femslash ship between Snow White and Ariel from the Once Upon A Time and Disney fandoms.

Ariel
Snow White meets Ariel during a time when she was countlessly running away from the Evil Queen, where they become fast friends; shortly after Ariel saves Snow from drowning after she runs off a cliff to avoid getting captured by the Evil Queen's guards. Once the mermaid got Snow to dry land, she tells her of the man she had saved before her and how she wishes to see him again, before showing Snow the invitation among her collected items that were dropped into the water and that he'll be one of the people attending the party. Snow wasn't sure how Ariel is going to take part in human party on land until Ariel turns her tail fin into a pair of legs and explains the legend of the sea goddess that has Ursula granting mermaids the ability to walk on land at high tide for twelve hours, every year, making the day of the party and who it is honouring feel like fate. Snow White is amazed by this and officers to accompany Ariel to the party for support.

The Jolly Roger
Years later in the modern world of Storybrooke, Mary Margaret (Snow White's curse name) and David Nolan (Prince Charming's curse name) were walking on the beach together until they see a group of people and went up to them to see what is going on and after Mary hears a man say that someone has just washed up on sure she asks them "who did?", and as they get passed the crowd Mary sees that the washed up person is none other than her friend Ariel. Mary was surprised to see her after so long and was worried that something bad had happened to Ariel since their last encounter and that she might had gotten herself turned into a monkey, Ariel reassures her that she didn't and that she is a girl who can turn into a fish. Ariel explains that she has been searching for Eric in every known realm and even under the sea to no avail, and had tried to find him in the Enchanted Forest when she heard everyone else went back there before coming back to Storybrooke, to see if she might had over look something. Mary felt sorry for Ariel and had felt bad that their lost memories have kept them from piecing a few things together, that could help Ariel find Eric, before she mentions the witch they are currently fighting against. Ariel asks them if Zelena could be the reason Eric disappeared, but Mary wasn't very sure that she is or not due to their lost memories until David recommended Hook as there is a chance that another sailor like him might know or have some kind of idea that could help them. The mermaid knew that Hook is a pirate and has had some bad history with him, but despite that she trusts Mary's faith in Hook and decides to trust him.

After Mary and David pervade Ariel with some clothes they took her to Hook, who told them that he doesn't know Eric. Feeling frustrated in how someone could just disappear, Ariel's words help Mary to come up with an idea since a few items have come back with them and one of them might belong to Eric, in which help could them to preform a location spell for the missing prince. Hook didn't want to help them any longer, but Marys asks him to go with Ariel encase he remembers something that could her friend find Eric. Since the mermaid had helped Mary in more ways than one and wanted to make sure that she and the others can help Ariel back. When the men went to talk as to why Hook doesn't want to help in front of Ariel, Mary keeps her friend company until David managed to convince him other wise.

Once Upon A Time

 * Ariel choses Snow over her chance to remain human, so she could be with Eric before he leaves, in order to save her from the Evil Queen.

Fanon
Because of the friendship that they formed in the Once Upon A Time series and are two Disney owned and based characters that are Disney Princesses who have been femslash in Disney crossover ships that focuses on its princesses, there are fans who use the ship and some of its titles in both fandoms.

Since Ralph Breaks the Interest is a canon Disney crossover that has a version of the two know each other, like their once counterparts do in the Once Upon A Time series, fans of the Disney side of the ship sometimes have Snow White and Ariel in the modern, style clothes that the netizen versions of them wear in the film.

On AO3, the OUaT side of the ship has 4 fanfics.

Fandom
FAN FICTION
 * Ariel/Snow White (Sofia the First) on FanFiction.Net
 * Ariel/Snow White (Kingdom Hearts) on FanFiction.Net
 * Ariel/Mary Blanchard (Once Upon A Time) on FanFiction.Net
 * Ariel/Mary Blanchard (Once Upon A Time) on FanFiction.Net

TUMBLR

Trivia

 * In the Disney film, Ralph Breaks the Internet, Snow White and Ariel appear as online versions of themselves known as "netizens", the inhabitants of the digital made world that lies within the real-life internet. Where they are two of the fourteen Disney Princesses that are from the expo-like Disney website, Oh My Disney.
 * They are two of the netizen princesses (and queen) that join in the "Neither do we!" with the rest of the motherless princesses.
 * They are two of the Disney Princess characters to appear in the first game of the Kingdom Hearts series.
 * As well as Ariel making her second reappearance one in Kingdom Hearts II and her third one as a summon character in Kingdom Hearts III, along a memory version of Ariel being seen in Kingdom Hearts: Chain of Memories. While Snow White makes her own reappearance in one of the prequel games of the series, Kingdom Hearts: Birth by Sleep.
 * Both Snow White and Ariel appear in the Disney Junior series show, Sofia the First, when the Amulet of Avalor summoned them to aid Sofia.
 * They are two of the limit time characters in Disney Magic Kingdoms.