A/n: inevitable mermaid AU bc come on, Luka lives on a house boat.

It seemed so cool, living on a house boat. Every time Adrien came over for band practice to just to hang out, he'd always notice something cool about the boat. Maybe that was just his desire to get away from the city and the fame he had talking. Living out at sea would definitely be more welcome than his life now. So much more quiet and private, sure there was a lot of maintenance owing a house boat, but it was worth it for the peace of the sea.

The family who owned the boat were cool too, the almost pirate like mother and musician twins who seemed quiet and reserved but around the right people came right out of their shell. At first, Luka was pretty reserved. He went to a different school and only knew Adrien and the rest of the classmates through his sister. But as time went on he opened up and now the band were the best of friends.

But there was something about him... he was secretive. Adrien couldn't talk, he was cat noir so he was always running off and being secretive himself. But Luka's way of being secretive was different. It wasn't like he was hiding a super hero identity (I mean, Adrien already knew he was Viperion) and it wasn't like he was hiding something like a grudge against someone. It was more like something deeply personal, at first Adrien thought sexuality. But wait, he was already out. Everyone knew he was bi.

So what was it? On one hand Adrien knew it was personal and he shouldn't pry. But he was a bit worried. The one thing that connected everything together though? Water.

He turned down swimming trips, beach trips and lake trips. Despite him living on a house boat and loving the sea. If it was raining he'd not leave the building he was in, not even to quickly rush from the entrance to the car or something. He always had a straw with him too, which at first Adrien just though 'oh yeah, metal straws better for the environment'. That was until he noticed he wouldn't drink without the straw, even if it was simple glass of water.

Something was up with Luka and water. Was he scared of it? Can't be, he literally lives on a boat. If he had trauma around water he'd be panicking in his own house.

So what was it? Unbeknownst to Adrien he'd soon find out.

"Got any 3s?" Adrien asked.

Luka gave him a sly look, down at his cards than up at Adrien again.

"Go fish" he replied.

"FUCK-" Adrien snapped, slapping his cards on the table.

How did Luka always fucking win? The musician snickered at him, tossing his cards down too.

"What wizardry do you do to always win?" Adrien laughed.

"No wizardry, you just have a skill issue" Luka teased.

"I hate you"

"No you don't"

"I don't..."

Adrien was the last one left to be picked up from band practice, Nathalie had called saying she was stuck in traffic. Not that either of the boys minded, gave them more time to goof around together.

"If you're just going to keep winning I'm not even gonna bother playing" Adrien said.

"Tch, sore loser" Luka teased.

"Shush! You'll just win again and you know it"

"True"

Card games over and done with for now, they decided to leave the cabin and head onto the deck where they'd be able to see when Nathalie arrived later on. It was sunset by now, and the reflection out on the water of the canals looked like a scene from a painting.

"You catch any fish out here? Or is it too inland?" Adrien asked, notching the nets on the sides of the boat.

"It's a bit too inland, but we sail up closer to the ocean every so often and fish there. Only ones you get down here are tiny minnows" Luka replied.

"You gotta being me one day, I've never actually been fishing"

They leaned against the railing, looking out at the water.

"It's a lot of waiting, but it's always fun feeling it in and seeing what you get. Like a weird game of gacha, expect the prizes are fish" Luka explained.

"That's one way to put it" Adrien snickered.

Before either of them could continue, the loud sound of a motor approached and cut them off. Up the canals some teens with jet skis were hooning around, before the two could even react they zoomed past at full speed causing water to splash up against the side of the boat and all over the boys.

"AHH! Oh come on..." Adrien scoffed.

"Shit- fuck, NO!" Luka panicked.

He looked down at his soaked clothes, then at Adrien and then at the water below them. He only had a few seconds to react, and it was clear to him the cat was out of the bag, there was no way he could hide this from Adrien now.

"You good?" Adrien questioned.

"Don't freak out-" Luka replied.

"Ok?"

Before Adrien could react, Luka jumped over the railing and landed in the water with a splash. Confused and kind of shocked Adrien looked over the railing, where Luka broke back up to the surface... hey, wasn't he just wearing his jacket?

"Ok listen- I can explain..." Luka said.

"What is-" Adrien began, onto the he cut off when he saw it.

A tail, a long blue-teal tail. Shimmering just under the waters surface where Lukas legs should be. Adrien just stood there in silence for a moment, taking it in. If he weren't cat noir he'd be more shocked. If a magic ring can turn him into a super hero then yeah sure, mermaids exist why the fuck not? He also put two and two together why it was better for him to jump in the water. On the deck anyone waking past could see him, in the water he could obscure his tail and swim off if needed.

"It's a family thing, clearly it's meant to be a secret. You can't tell ANYONE ok? Please Adrien don't tell anyone, I'll end up siren sushi..." Luka begged.

"Woah- ok, yeah I'm not telling anyone. Don't worry... but how? Since when? Huh?" Adrien stammered.

"Uh... ok 1, not sure. It's just a family thing, we're all Merfolk. 2, since I was born and 3... understandable reaction"

Adrien climbed over the railing, standing on the small ledge at the back of the boat meant for getting in and out of the water, ducking down to get a closer look. The fins and fluke were slightly lighter than the body of the tail, fluke big and wide with flowy fins on the hips and ankles. Slightly dotted with darker navy markings up the sides. The scales faded into skin as they came up to the waist and connected to the rest of his body. Luka allowed the mesmerised blonde to reach into the water and touch his tail, his fingers slightly tickling at the touch.

"So that's what you've been hiding... it all makes sense now" Adrien muttered.

"I felt bad keeping it from you... but it's just one of those things you have to do I guess. Just, keep it between us ok? I'll show you all the cool underwater stuff one day alright?" Luka replied.

"Promise"

Adrien held out his hand for a pinky promise, making Luka smile and some of the anxiety leave his body. He knew he could trust Adrien, they knew about each other's hero forms after all...

"What are we five? Pinky promise" Luka joked, linking fingers and shaking on it.

"There's soooo many fish puns I can make now" Adrien teased.

"Don't overdo it or I'll steal all your shinies"