Another reason might be environmental disaster in a fanfiction. If the ocean was being polluted at an alarming rate and Ariel tried to fix it but was exposed to too many toxins. As she took her last breath, she would be sad about the future of her ocean home and the creatures she loved.
In a fan - created backstory, Ariel could have a pre - existing condition that was made worse. Maybe a magical illness that was always there since she was born. And when a certain event triggered it, like overusing her voice (if there was a twist in the story), she would take her last breath, leaving behind a legacy of a brave and curious mermaid.
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.
It could be that Ariel has been poisoned by some dark magic from an enemy of the sea. As her strength fades and she takes her last breath, she looks towards the surface of the ocean where she first saw Eric. In her last moment, she remembers all the adventures she had on land and underwater. Her last breath is a testament to her courage to explore and love beyond the boundaries of her own world.
Ariel's last breath could be a turning point if it leads to a magical resurrection. For example, her love for Eric and the sea could be so strong that it triggers some ancient magic. Her last breath releases a powerful energy that not only brings her back to life but also changes the relationship between the humans and the mer - people. It could be the start of a new era of understanding and peace.
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.
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 the fanfiction, a romantic plot could involve Ariel getting the ability to walk on land permanently. Eric then takes her on a tour of his kingdom, showing her all the beautiful places. At sunset, he takes her to a cliff overlooking the ocean and proposes to her, making it a very romantic scene.
She might step on a sharp shell on the shore. This could be a turning point in the story as it makes her realize the differences between the ocean and the land. It could lead to her having to seek help from a human, which in turn could start a new friendship or a romantic connection.
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.