Something that is really upsetting about the ziam fic world is the lack of Mermaid AUs.
Think about it - Liam, a sailor from the 18th century, was turned as his ship overturned and a young mermaid named Niall took pity on him, saved him by making him a mermaid and as a result, he gets eternal life as long as he doesn’t leave the water. Liam is quite happy with this at first but then his young mind grows curious and he starts to drift a little closer to the shore each year.
It’s the 21st century now and mermaids are thought by most to be a distant legend so Liam’s not too worried. But then one day, when he’s swimming to the rock pools where he likes to people watch from, he sees this boy. This terrified looking boy, who’s just sat there with his jeans rolled up to his knees.
They awkwardly just stare at each other until Liam dives away and swims back to his friends and pretends it doesn’t happen.
But of course, he’s too curious to stay away. So he swims back about a week later and finds the boy there again, looking as surprised and nervous as Liam feels.
It’s awkward at first because neither of them know what to say and Liam shouldn’t be this willing to just show himself to this boy but he’s perfectly okay with it for some reason. But then they make slow, tentative introductions and Liam finds out the boy’s name is Zayn, he’s 21 and he can’t swim. Liam, in turn, explains that he has no idea what his real age is anymore and he’d really, really appreciate it if Zayn didn’t share his secret. Zayn giggles and says he doubts people will believe him anyway.
They keep meeting in secret for a good few weeks, and Liam realises he keeps wishing that Zayn won’t actually leave him. But then the summer ends and the sea gets colder and Zayn tells him he has to return to uni, despite the fact that he can’t stand it anymore and he just wants to be a singer and he decided a long time ago that he doesn’t want a proper job. He doesn’t want responsibilities and Liam hasn’t had a responsibility for three hundred years so he doesn’t know what to say.
On the last night before Zayn has to return, he doesn’t want to go out with friends, he comes to find Liam and they both cling to each other awkwardly until Zayn just pushes himself into the water without a warning and Liam grabs him, holds his spluttering body above the water and clings to him.
"What are you doing?" he shouts. "You can’t swim, Zayn!"
"I want you to turn me," Zayn begs. "Turn me, give me a life free from responsibilities and let me just be with you."
Liam wants to cry. He tries to explain that it’s not worth it - he lost his family and his legs and he longs to be back on the earth more than anything but he can’t. And Zayn does cry because he doesn’t want to go back and he wants to be with Liam because he’s fallen for him and he can’t imagine a life without him anymore. And Liam cries because it’s the same for him, but he can’t ask Zayn to turn for him, to give up his life and his family and everything, he can’t.
Zayn goes back to uni and Liam goes back to Niall and it’s not fine at all but Liam makes do. He meets new mere friends, beautiful mermaids called Jade and Jesy and then two mermen called Louis and Harry, who explain one night when they’re drunk on an overturned crate of wine they found that Harry was a human once too, but once he and Louis realised they wanted to be together he made Louis turn him, made him a merman despite all Louis’s protests. They seem happy, for the most part, and Louis says he could never regret what gave him Harry, even if he does sometimes wonder if Harry misses the shore or his old life. He just makes an effort not to mention it.
A few months go by until Liam sees Zayn again. It’s cold now, nearing Christmas, he imagines, and he returns to their rock pool for no reason other than nostalgia. But Zayn is there, of course he is, bundled up in lots of thick layers and with a sad smile.
They don’t say anything, but Liam pushes himself out of the water and kisses him before Zayn can protest. Their lips mould together and it’s cold and warm, wet and dry, and then Liam’s sinking, sinking…
Because he finally got his true love’s first kiss and whatever held him in the water has vanished. His legs are back, but he’s forgotten how to swim with them so he starts to sink… but Zayn is there, one hand clinging to Liam and the other clinging to a slippery rock but it’s not enough…
But then Liam’s being pushed up, up, up by something else. Hands are on his back, raising him out of the water and he’s gasping for air, limbs flailing and uncoordinated as Zayn grabs for him again and hauls him out as best he can.
Niall and Louis are there, watching him, saving him, shouting at him to wake the fuck up, Liam, and he does and the first thing he sees is Zayn. Beautiful, wonderful, human Zayn, who he can now join and live with and love as he’s always wanted to.
Zayn learns how to swim, and Liam remembers. They see their friends often. Eventually Liam finds out that if he stays in the water long enough, his tail will reappear until he’s dry again. It’s nice, but not as nice as living with Zayn, sharing his life with Zayn, having Zayn love him in return. He wouldn’t swap that for his tail again, or anything else at all.