Author's Notes: Weird story is weird. It can blamed on several things, but mostly it was inspired by trolling through the "Mermaid" tag on PotterSues. I just decided to do something about the canon merpeople (who are pretty interesting, really) rather than make up something about pretty ones who can turn into humans when they dry off or something.

This was originally a one-shot, but it's about 10,000 words now so I'll publish it as three or four chapters instead. I hope somebody likes random OC friendship fics/xenofiction enough to enjoy!

The Hogwarts boats sailed overhead twice every year, about a dozen dark shadows disrupting the calm surface of the water.

Nobody down in the village really noticed when they passed. They were like airplanes flying above a human town, distant and only vaguely interesting. The merpeople had occasional issues with the wizards up at the school, but the boats didn't really bother anyone and were subsequently ignored.

Lacu had not even realized that they would be going by tonight, though now that she saw them, she was fascinated. They were such an interesting way for humans to compensate for their inability to swim right.

She kept pace with the little fleet, swimming higher up to catch a closer look. For a moment she even thought of breaking the surface, but she hesitated, coming to a stop and allowing the black shapes to pass over her head. She was startled as something suddenly came through from above, and she saw five stubby human fingers sail by, almost close enough to pass through her hair. They vanished just as quickly.

"Lacu!"

She turned around and down to see her little brother Lagu, arms crossed as he made a face at her. "Can't you tell it's dark out?" he snapped. "Mum wants you home for dinner!"

She frowned. "Tell her I'll be there in a few minutes!"

He didn't answer, just swam in an arc and headed back toward the village. Lacu cast one last curious glance at the boats just as they vanished into the night.

"Hey, the teacher said to keep your hands inside the boat! I'm telling!"

"Don't be a jerk!" Lily Potter snapped, even as her cousin Hugo Weasley hastily removed his fingers from the water.

"But the teacher said—"

"There was something down there," Hugo interrupted, squinting down at the black surface of the lake.

"It was probably the giant squid!" said the boat's fourth occupant excitedly. "My brother said that the lake has a giant squid and that there are unicorns and werewolves in the forest!"

Hugo normally would have been quite happy at the prospect of seeing any of those things, but this time he merely frowned. "It didn't look like a squid. It looked more like a person."

"There are merpeople in the lake," Lily said knowingly. "My dad said so. He actually went into the lake and met them, during this fourth year, I think!"

"Really?" Hugo's eyes remained fixed on the water, but a manic grin spread over his face. "Cool. HEY HAGRID!"

"Huh?!" The enormous man was two boats ahead of them, and he turned around so fast that his dinghy almost capsized. "Wassa matta?! Ev'ryone alright?!"

"Yeah! I just wanted to know if we're allowed to go swimming in the lake!"

Hagrid stared for a moment. "Wha', righ' now?!"

"No, just whenever!" Hugo said cheerfully.

It turned out that the answer was "no." Hugo pouted, looking down at the glassy surface again.

He wondered how long it would be before he found an opportunity to break that rule.

Evening was Lacu's favorite time to go swimming off by herself, because that was when overwater was at its most beautiful. The orange-pink sky reflected wonderfully on the surface, and as the colors faded to gray the castle would light up, with the strange shadows of its inhabitants moving around in its windows. A huge cloud of birds—owls, they were called—would swoop down from the school to go hunt in the forest, flying almost as one giant creature. Unfortunately she could never watch for long before her parents or her brother came looking for her, calling her in for the night.

Lacu was heading back now, but only slowly, idly picking pebbles out of the lake-bed and adding the nicer ones to her seaweed-rope necklace. She was in the area filled with boulders—actually old debris from the war that had happened at the school twenty years earlier—when she heard a sudden commotion. She turned, swam around a large block of stone and saw it an unexpected sight: a human boy swimming in the water, being attacked by four snickering Grindylows.

The human looked as odd as any other, with legs where his tail should be and weird pinkish-white skin. He didn't seem to be wearing as much fake skin as humans usually did, though, keeping only his waist and the top of his legs covered. His hair was long and red, and one of the Grindylows was pulling on it. The other three had taken hold of each leg and an arm, and they seemed to be pulling the boy toward the bottom of the lake. He was struggling, and his cheeks were puffed out and turning red.

The merpeople did not generally think of Grindylows as anything but pests; at worst they could hurt a small child, but one tail-whack from an adult would usually send their entire school fleeing. However, Lacu quickly realized that humans were a different story—not only were they slow and clumsy in the water, they could only breathe surface-air, so being dragged down to the sand was a legitimate danger for this boy rather than a petty annoyance.

As soon as the thought hit her she swam forward, reaching for the small bag that she kept tied around her waist. Inside were a collection of trinkets, but also a single heavy rock that she kept for tasks such as this. She pulled it out and held it high, bringing it down onto the nearest Grindylow's hand.

"Let go!"

Lacu heard an unpleasant CRACK! as the stone made contact, breaking the Grindylow's strong but brittle fingers. It let out a cry and released the human's leg. The other Grindylows turned to Lacu and let out fearful cries—almost as one they abandoned the boy, who began to flail toward the surface in a way that was almost comically awkward. Lacu, now positioned below him, tried to push him up by his leg and didn't really help much.

She heard the human's head break the surface of the water. She was pretty sure that was all he needed to be able to breathe again, but she swam up after him just to be sure.

The human was indeed breathing again, and quite vigorously, too. "Well, that—wasn't—fun," he gasped. Lacu was momentarily taken aback—she knew that humans could speak water-talk above the surface, but it was still strange to hear. The human tried to wipe the damp hair out of his face, and Lacu noticed tiny reddish-brown dots all over him, going down his neck onto his shoulders. For a wild moment she thought they were Grindylow bites, but there were far too many of them, and they did not seem to be bothering the human at all.

The boy seemed to notice Lacu for the first time. His eyes suddenly went wide, and his mouth opened, revealing strangely flat and square-looking teeth. There were some sort of metal decorations on them that shone in the dimming twilight.

"Oh, wow. Wow! You're a mermaid!" He seemed to have quickly gotten over his near-drowning. He suddenly leaned forward, and Lacu instinctively leaned back. "You helped me with those whatchacallems—Grindylows back there, didn't you?"

Lacu nodded. She opened her mouth to speak, but before she could the human's hand suddenly splashed out of the water, extending toward her and nearly hitting her in the face.

The human waited expectantly. Lacu hesitated, then reached out her arm in the same way. The human frowned, then grabbed Lacu's hand in his own and shook it vigorously.

"Thanks for the help back there! My name is Hugo Weasley! What's yours?" He spoke very fast and very loudly.

Lacu hesitated for a moment, unsure if she should answer. Her parents usually told her to stay away from students from the human school. It wasn't quite that the merpeople and the wizards were on bad terms, but there had been various incidents of one kind of another over the course of the centuries. The two sides generally tried to stick to themselves.

"(My name is Lacu)," she said finally, and the boy called Hugo Weasley suddenly drew back, letting go of her hand. Lacu was startled in turn, and the boy began to rub his ears, frowning.

"Oh...sorry. You don't speak English, do you?"

It was Lacu's turn to frown. "(I can't speak water-talk above the surface, if that's what you mean.)"

"I'll take that as a 'no,'" Hugo Weasley said. He rubbed his chin for a moment, then pointed at himself. "MY NAME IS HUGO WEASLEY! HYOO-GO WEEZ-LEE! WHAT'S YOUR NAME?"

"(No, I—)" Lacu hesitated, then lowered her head into the water, submerging it up to her nose. "My name is Lacu," she repeated, in water-talk.

Hugo Weasley blinked, then turned his head so that one ear was underwater. "Say that again."

She did. Hugo Weasley's eyes widened again, and he flashed another manic grin.

"Cool! How do you do that?"

She was about to ask how he managed to use water-talk when he was above the surface, but Hugo Weasley was suddenly distracted; Lacu followed his gaze and saw red sparks back at the shore. "Darn it. My friend's saying I have to go now." He hesitated, then turned back to Lacu. "Hey, can I see you again tomorrow?"

"(Tomorrow?)" She was so surprised—about this whole conversation, really—that she forgot he couldn't understand surface-talk. He seemed to get the gist, though, since he nodded even as he began swimming back to shore.

"Yeah. I'll probably start coming later than this, like after nine. I'd like to come during the day, but we're not really supposed to swim in the lake and I don't want to get caught. Plus I'm trying out for Quidditch tomorrow and we might have practice in the evening. Anyway, see you then!"

He waved, turned and paddled the rest of the way to shore (which again, looked clumsy and ridiculous). It was getting properly dark now, and Lacu watched him for only a moment before diving back under the water and racing home.

She thought about his offer as she swam. She really shouldn't come back. Rescuing a human from drowning was one thing, but making plans to meet one...not to mention after she was supposed to be in bed...

Lacu was a nervous sort of mermaid, and she didn't like to break the rules, but she was also very curious by nature. She knew she shouldn't see the human again, but something about his weird, dotted face with its goofy, flat-toothed smile just seemed to be screaming for further examination.

Miles made a face. "I don't want to go back tonight, Hugo. It's no fun just staying on shore, staring at my watch."

"Then you should have come in with me!"

"You just said you almost drowned!"

"Well, yeah," said Hugo, with an airy wave, "but I could have fought off those Grindylows if I had my wand with me. Plus my new mermaid friend helped me out!"

Miles' scowl deepened. "I still say she didn't look like any mermaid I ever saw," the Muggle-born boy grumbled. "She looked more like a sea-monster herself."

"But she's a nice one!"

Sure enough Hugo sneaked out of the Ravenclaw Common Room alone that night, wrapped up in one of his dad's older and rattier Invisibility Cloaks ("He won't even notice it's gone" Hugo had decided when he packed a few weeks before). Once at the lake he stripped to his bathing-costume and waded up to his waist, shivering slightly and scanning the immediate area. "Lacu?" he called, trying to be loud and quiet at the same time.

Half of a head emerged hesitantly out of the water. Hugo grinned, swimming over to her. "Hey! How are you?"

He heard something muffled by the water. He crouched down and turned his head. "Say that again?"

"Good," Lacu said nervously.

"That's good. I'm actually kind of lousy today," Hugo said, his exuberance suddenly turning to bitterness. "I tried out for my House Quidditch team and only got on reserves."

"Your what?"

"Quidditch team. Oh duh, I guess you don't have Quidditch underwater! It's this game..."

Hugo's bitterness vanished as quickly as it had appeared, and he went off on a long tangent about how Quidditch worked and how you played and why the Chudley Cannons were much better than the Falmouth Falcons and his cousin Louis just had to learn to deal with it. Lacu, though still wary of this whole meeting, took advantage of a lull in his ramble to talk about a game merpeople played that was sort of similar, except you swam instead of flew and some of the terms were different. Soon the two were speculating about whether or not the games were related somehow, before Hugo went off on another tangent about how the Cannons could beat the Falcons even better underwater because ships use cannonballs but obviously falcons can't swim.

Eventually the conversation died and the two were just floating in silence, which for once Hugo didn't feel the need to fill. He cocked his head to one side, trying to make Lacu out in the moonlight. Miles had a point—she really did kind of look like a sea-monster, with her gray skin and her long green hair and her eyes that looked bigger and yellower than a human's. She showed her teeth when she smiled, which were dirty and pointed like fangs. But it was a nice smile anyway, and it reached up to her eyes, making her whole weird face seem kind and sincere.

"You know, you're really cool."

Lacu blinked, then put her mouth below the water again. "Um, thanks," she said sheepishly.

He looked around. "Huh. We've kind of drifted a long way from shore. Hey, let's have a race! First one back there—whoa!"

Instead of racing, Lacu grabbed Hugo by the wrist and began to pull him back toward shore, swimming far faster than he could have managed. It was a rough ride with his head emerging and sinking into the water every few seconds, but he laughed the whole time and didn't care how much water he swallowed.

By the time they stopped swimming, Lacu was laughing too.