Feinny i really like https://toyhou.se/780961.riyad- and i think he would make a really good friend for her. I just got her and haven't had time quite yet to get her profile set up with artfight and coding on mobile being not fun. but they're able to go freely between water and land, and she frequents land. she's always bringing stuff back for him to try to get him interested in joining her, even once. he's stubborn and uncertain about the city residents, and he's very stuck in his ways as his parents told him for years never to go to the surface, but she's very determined. he can be a very good leader, but sometimes clueless about certain things and a bit childish at times. he greatly enjoys the cute things she brings back for him and keeps them all in a big crate that fell into the water, or just around his living space if he really wants to see them more often. there's also competitions between all the mermaids to show who has the most land items collected! technically only items that were dropped into the sea and items left near the water are supposed to count, but it's not a super regulated rule and just goes off of honor system. he wins frequently. he can occasionally be found just at the edge of the water, but usually flees if he sees anyone around, which makes it difficult for serena to introduce him to her friends. he'd be super fascinated by everything around him if he decided to join her and go to the surface, and would probably have his hands full of stuff to bring back with him and she wouldn't be able to tell him no when he's so excited.
thank you for considering! my favorite of your characters is probably altair, i really like male characters with long hair..