The plot might start with Serena finding a strange, enchanted shell on the beach. When she touches it, she is turned into a mermaid. In this new form, she realizes she can communicate with water - type Pokemon in a different way. She embarks on a journey to find the origin of the shell and the power that transformed her. Along the journey, she makes new friends among the mermaids and Pokemon, and together they face a powerful villain who wants to use the shell's power to take over both the sea and the land.
In a fanfiction, Serena as a mermaid might be part of a mermaid kingdom that has a long - standing feud with a group of sea - dwelling Pokemon. Serena, being kind - hearted, tries to bridge the gap between the two sides. She uses her charm and the skills she has learned in the Pokemon world to negotiate peace, all while looking stunning with her mermaid tail and long flowing hair.
One possible plot could be that a Pokemon, like Vaporeon which has a mermaid - like appearance, gets transported to the world of The Little Mermaid. It befriends Ariel and helps her in her quest to understand the human world. Vaporeon could use its water - based powers to protect Ariel from Ursula's evil plans.
Love and relationships are also quite common. Whether it's her relationship with Ash in a new light because of her mermaid form, or new friendships she forms with other water - type Pokemon. In some fanfictions, there's a theme of acceptance. Serena has to deal with how others will accept her as a mermaid, especially those who are close to her like her friends and family in the Pokemon world.
One possible plot could be that a Pokemon, like Vaporeon which has a mermaid - like appearance, gets transported to the underwater world of The Little Mermaid. It could make friends with Ariel and help her in her adventures. For example, Vaporeon could use its water - based powers to protect Ariel from Ursula's evil spells. Maybe it could also communicate with the sea creatures in a unique Pokemon way, which would be fascinating for Ariel and the others.
One possibility could be that Serena gets angry when she is constantly overshadowed by other trainers in a big tournament. She might feel that all her hard work is being ignored, so she gets angry and decides to train even harder in isolation to prove herself.
Maybe Serena discovers the exciting world of Pokemon and gets completely hooked. She could start by seeing a Pokemon battle and being in awe of the power and beauty of the Pokemon. Then she might decide to start her own journey to catch different Pokemon, facing various challenges along the way.
Maybe it could be about the little mermaid's new adventure in an undiscovered underwater kingdom. She might meet new friends or face new enemies there.
One way to find good Pokemon Serena Mermaid fanfiction is to search for it on Tumblr. There are often communities dedicated to sharing and discussing such fan works. A lot of these fanfictions might incorporate elements of Serena's journey in the Pokemon series, like her contests, but with the added twist of her being a mermaid. It could be really interesting to see how her mermaid abilities interact with her Pokemon skills.
One possible plot could be that Serena and May meet during a Pokemon journey. They initially start as friends, sharing their experiences and knowledge about Pokemon. As time passes, they realize they have deeper feelings for each other. They might face some challenges from the Pokemon world, like dealing with a powerful villain who tries to stop their relationship because he believes it's against the norms of the Pokemon trainers' world. But in the end, they get married and continue their adventures together with their Pokemon.
Well, it could be that Ash finally realizes his deep feelings for Serena during a grand Pokemon event. Maybe they are in a beautiful, flower - filled meadow near a Pokemon Center, and Ash gets down on one knee with a Pokemon - themed ring, perhaps made from a shiny Pokemon scale or something unique.