Perhaps in some fanfiction, Ariel's death could be due to the pollution of the ocean. As she is a mermaid, her home is the sea. If there is excessive pollution, it could make the sea uninhabitable for her and the other sea creatures. She might succumb to the poisoned waters while trying to find a solution to save her home.
Prince Eric would be devastated. He fell in love with Ariel for her beauty, both inside and out. Her death would leave him heartbroken, and he might become a recluse, spending his days mourning by the sea. He could also become a bit of a crusader, trying to do things in Ariel's memory, like cleaning up the ocean or protecting mermaids.
In some fanfictions, Ariel's death might be a tragic result of a broken heart. Maybe after Eric chose another, Ariel, in her deep despair, could take her last breath while looking at the sea that she once left for love. It's a really sad concept as she sacrificed so much for a love that didn't end well.
Perhaps in the fanfiction, Ariel and Eric get married and have to deal with the cultural differences between the underwater world and the human world. For example, Ariel has to learn the proper etiquette in Eric's kingdom while Eric tries to understand the unique traditions of Ariel's mermaid family.
There are several possible reasons. Maybe she has lost something precious in the fanfiction. It could be a magical item that was important for her connection to the sea. Or perhaps she has had a fight with a friend or someone she loves. This emotional distress makes her break down in tears as she tries to deal with the situation.
Ariel could die due to a tragic accident. For example, she might be exploring a sunken ship when it collapses on her. Unable to escape in time, she gets trapped and runs out of air. This sudden and unexpected death would shock those who knew her, both in the underwater realm and among the humans she had befriended. It would also lead to a great deal of mourning and could potentially drive Prince Eric to seek revenge on those he believes are responsible, like pirates who might have looted the ship and weakened its structure.
In a fanfiction scenario, Ariel takes her shoes off when she reaches the shore. As she does so, she feels a strange connection to the land. It's as if the act of removing her shoes makes her more attuned to the human world. She starts to learn about different types of shoes that humans wear and even tries to make her own, using materials from the ocean. This leads to some humorous and heartwarming interactions with local villagers.
Perhaps in a fanfiction, Ariel and Eric will have a family of their own. They will raise their children to understand both the land and the sea, creating a unique bond between the two worlds.
One possible fanfiction could be that Ariel and Eric discover a hidden underwater kingdom that was lost long ago. They embark on a journey to learn about its history and find that it holds the key to a magical power that can save both the underwater and land worlds from a new threat.