A/N: A bit of inspiration here from Mako mermaids/H2O and all those other lovely transforming merpeople.

Beta love goes out to TheFrenchPress 3

"Peeves!" came the screech, echoing through one of the lower corridors.

Severus Snape came billowing out of his office like a great black cloud. The students had left only the day before and the resident poltergeist had, out of boredom, taken to targeting the staff instead.

He heard a splash followed by a wet slapping sound. Water was already trickling in his direction, so he hurried onward, towards the scene of the disaster, spelling his shoes not to slip on the wet stone floor.

"Peeves, come back here, you little bastard!" shouted a voice he knew all too well.

Hermione Granger had finished her apprenticeship under Flitwick that year. Apparently she'd done quite well and after another year would be ready to take over the position, but all Severus wanted was for her to leave him alone. She was always hovering around on the weekends, asking a million questions about whatever he happened to be brewing.

"Shouldn't you be bothering Filius?" he asked her nearly every time without fail.

"Just because I'm going to be a Charms professor doesn't mean I'm not interested in other things."

"Go bother Minerva then, or Aurora."

"You know they're busy with their own apprentices."

"If I find one of my own, will you go away?"

"I would, but you and I both know you don't actually want one."

Over and over, like the scene from a bad movie that you have to endure to get to the enjoyable part (or did in the days of film anyway), she just kept turning up, asking questions and invading his space. Merlin, she was frustrating. And yet he couldn't bring himself to actually lock her out. For some reason he knew it would be on par with kicking a puppy and while he might be the surliest wizard in the castle, even he couldn't stoop so low. Besides, sometimes she had good ideas. Not that he was ever going to admit that aloud.

When he rounded the corner, he first thought that Peeves had somehow dumped a giant fish of some sort. But that was unlikely because the fish was sobbing and had impossibly long hair. The last time he'd studied creatures, magical or otherwise, no fish had hair.

He drew nearer to the large pool of water and noticed the beautiful scales were in shades of greenish-blue and pink, the large caudal fin now flapping gingerly as it flung droplets of water into the air. And that was when he saw a hand reach out from beneath the mop of long dark curls, palm pressing against the slippery floor. Definitely not a fish, then.

There was the sound of frustrated sobbing interspersed with things like, "I'm going to exorcise him!" and "Miserable little gobshite!"

He rushed toward the creature without even thinking. What was he even doing? Just as he drew near, she pushed her bare torso from the floor and he skidded to a halt when her face turned in his direction.

"Granger?" he exclaimed, dumbfounded as he looked her over.

Her normal mane of curls had lengthened considerably, but even so it was obvious that she was semi-unclothed. Yes, that was the word that he preferred as he gulped, very thankful that he was in his teaching robes. Stars above, she was a beautiful creature. Even flopping around as a half-fish in the middle of a dank corridor.

She flicked her head and hid herself behind her veil of curls.

"Go away, Snape. I just need to dry out."

"Drying spell?"

"It makes my scales brittle."

"Right." He should have known that. She simply had him flustered was all.

"Why are you like this?"

"Because I'm cursed, you miserable git, now leave me alone!"

"Do you ever do as I ask?"

"No," came the uneasy reply.

"Then why should I? Tit for tat, Granger."

"If Peeves were alive, I would kill him."

"As would so many," he agreed and with a swish and flick of his wand, she rose gently into the air.

"What do you think you're doing?"

"Being helpful," he grunted. He floated her along the corridor carefully, trying to ignore the way her fins were undulating in the air, shimmering in the torchlight. It was difficult.

He opened the doorway that led to his quarters, wondering if that was a wise thing to do. Of all the wretched things to happen today; at least there were no students around and Minerva was unlikely to come looking for him in the event he didn't make it to dinner.

"Do you remember how I attempted to send you away last month?" he asked.

"You do every time, but I'm not convinced that you really mean it or you'd start locking your door."

She was infuriating sometimes.

"In some cultures, a closed door is as good as a locked one," he responded, rolling his eyes. "There is such a thing as privacy."

He flicked his wand toward an adjacent room and the sound of running water echoed in the room.

"Is this where you live?"

"You're incredibly nosy for someone who can't do anything but flop on the floor at the moment."

"It obviously is. No one else lives under the lake except the Slytherins." She was staring up at the murky light that filtered through the bevelled glass covering part of the ceiling.

He spelled his buttons undone with a bit of personal charm-work and shrugged out of his robes as they slowly headed toward the sound.

"The day we brewed with gillyweed, Granger," he began explaining.

Her head swivelled toward him, her whiskey-coloured eyes taking him in as he shed his waistcoat. He tried in vain to ignore her blatant staring.

"Yes?" she asked. She sounded nervous.

"Do you remember what happened?" he asked, pulling his gaze from her.

"There was something like… a cloud? Vapour?"

He used the spell again to unbutton his Oxford. He took great pleasure in buttoning it up by hand each morning, but could never be bothered at the end of the day.

She was practically squirming in mid-air, and he had the notion to hurl her into the next room if only to stop her. Unfortunately the tub had been drained for cleaning and would take several minutes to fill.

He toed off his shoes and pulled off his socks. The chill of the stone floor cut through the rugs beneath his feet, and he remembered why he never went without shoes or slippers.

He walked ahead of her and lit the lamps in the enlarged bathroom. The tub alone took up half of the space. It was roughly the size of the one the prefects enjoyed. Sometimes he had snuck in there while he was a student. No such luck for the professors: they had their own baths, but those were made for humans, not creatures. It wasn't until after the war that the castle decided he should have a proper place to bathe.

Since he had still not managed to find an antidote, it was this or a wash up in the sink. The water now high enough, Severus levitated her in from the other room and dumped her unceremoniously into the giant bath. She shrieked and landed with a splash. Smirking, he took the occasion to unbutton his flies and strip off his trousers.

"What in Godric's name do you think you're doing?" she shouted after spitting water out of her mouth.

It was just far easier to show her than explain.

"Turn your head, you daft witch," he snarled. Surprisingly, she did as he asked.

He stripped off his trunks and hurriedly stepped into the pool.

His legs suddenly fused together, the dark hair on them disappearing beneath dark green and silver scales. He dove beneath the surface, letting the warm water soothe his aching muscles. When he came back up for air, she was staring at him again.

"Explain." Her arms were folded across her chest as she bobbed in the water. A ripple of something unknown passed through him as he caught another glimpse of the soft mounds that were gently crushed by her arms. Clearly he had not entirely thought this through.

"I've been trying to find an antidote for some time. I didn't have the supplies nor the time before, but now that the war is over, I am afforded certain… luxuries. Ones that you have been encroaching upon."

He paused and glared at her. It was better that he remained angry in order to block out other emotions, other thoughts.

"You could have told me!"

"So I could become some curiosity for you?" he sneered. "The day with the gillyweed, I was recreating the first potion, the one that went wrong. But I had forgotten about the vapour. You inhaled it and… well, you know what happened. You weren't supposed to be there, but you are incorrigible."

"How am I ever supposed to bathe again?" she whined.

"You can't until I can find an antidote."

"What if I helped? Wouldn't it be faster if we were both doing some of the research?"

"You think you'll fare better than me?"

"How long have you been like this?"

"I was young." Actually, it was the summer before he started school, but she didn't need to know that.

"Let me help you." She had changed her tone and that grated against him all the more. "Please, Snape."

The way she said please was so wrong. So very wrong. And why was she swimming closer? He edged backward until his tail bumped against the tiled walls of the tub.

"Stay away from me," he hissed.

"You could have let me dry off in the corridor."

"It would have taken hours. Someone else would have found you."

"Would that have been a problem?" She came closer still.

"It would have been when it came to light that it was my fault Flitwick's shining star was now a creature."

"How do you dry out?"

"The floor in here is heated. It doesn't take long. Maybe ten minutes."

"So why didn't you just sit me down me on the floor then?"

"I wanted to show you. Easier than explaining. Not that you listen to a word I say anyway."

"Well, now you have my attention, Severus. Can I call you Severus now? You're the only professor who hasn't extended me that courtesy."

"I'd rather you didn't. Snape is just fine." Merlin, what was her problem? He accioed a towel from across the room and scooted out of the tub. His tail glistened as rivulets of water poured from him. He needed space. He needed to keep her from touching him. He kept his long tail in the water.

She slid out of the water and sat directly next to him, dripping on him. She brushed against his wrist fins and it made him feel queasy. He dug his nails into the palms of his hands and stared at the wall opposite them.

"So, how did you come by this?" she asked, gesturing at the enormous bath. She was either oblivious to his irritation or just didn't care. He guessed it was more likely the latter.

"The castle did it."

"When?"

"After the war." He didn't know why he was answering her. He really needed her to leave, not continue prying.

"So all those years…?"

"Yes," he snapped, cutting her off.

She pushed some of her curls back from her face, heavy with water, and he made the mistake of looking over at her. Salazar help him, he did not need that glimpse of her perfectly round… He swore aloud, making her start.

"What happened?" Her voice was hushed, concerned even.

"Nothing," he grunted.

She sighed and scooted back from the edge so she could lift her tail from the water.

"I suppose this isn't the worst potions accident to ever befall me. Being a human-sized cat was far worse. I was coughing up hairballs for weeks."

"Ah, yes. Well now you know why Polyjuice isn't a beginner-level potion."

"I'll have you know that Ron's and Harry's worked just fine. I just grabbed the wrong hair is all."

"Yes, well, if I had known it was you, I would have tweaked the antidote a bit—left you with cat ears or some such as a lesson."

"Instead you've turned me into a mermaid."

"Genus atargatæ, species syreni," he corrected.

"Severus…"

He ignored her. If she was going to repeatedly call him by a name she had no right to, he equally had the right not to respond. He began towelling his hair dry as he ruminated. Why was it always her? She had set fire to his robes, stolen from his stores, nearly got him killed by a werewolf - her favourite professor, no less - tried to prove just how smart she was in every single class… She was a menace. And now she was a mer-menace. He smirked to himself. That would be her new moniker in his head.

"Severus…" she called again from behind him.

No, mer-menace, he thought in his head. Not today. He scooted back to flick up his tail and stretch it along the tile floor. He threw his towel over his lap as he laid back, waiting for his tail to transform back into legs.

"Snape," she said hesitantly. "Do you ah… have another towel I could borrow?"

Dragon dung. He only had one towel. Why hadn't he thought this through more thoroughly? He could not have a naked Granger sprawled on his bathroom floor. In fact, he didn't want a clothed one there either.

"Accio bathrobe," he called out. A fluffy terry cloth robe came hurtling towards him from its hook just outside the door. He tossed it in her direction without looking.

"Thank you," came the soft reply. Too soft. He really needed her to leave. This was bordering on too inappropriate for his taste. Mostly because he was running out of self-control.

"Godric, Snape, I never knew you had so many scars."

His head automatically swivelled in her direction to scowl at her properly. Thankfully she was already wrapped up in his robe, sitting on the floor. He would have to send it straight to the laundry when he got it back. He didn't want to know what she smelled like up close.

"It's none of your business, Granger."

She crawled over to him to take a closer look.

"Stay back!"

"I was only curious," she stated casually, sitting back on her haunches.

"I'm not an object for your amusement."

"I'm not amused," she argued. "Have you tried some of the newer scar creams? I found one that's been very helpful."

"No, I haven't bothered."

"I'll bring it by later."

"Only if you must," he sighed.

"Do you remember that scar Dolohov left me with? In the Department of Mysteries?"

He had tried to block that one out. He'd felt so guilty.

"Well, look now," she continued, opening the top part of the bathrobe.

"I don't want to…"

"Don't be such a prude. I'm just showing you my scar, or what's left of it."

His face felt suddenly warm. But she was right. The scar, once an angry purple, was a pale lavender.

"Why are you like this with me?" he blurted out.

"Like what?"

"It's like… it's like you have no boundaries with me."

Lips pursed, she looked at him thoughtfully. "I wanted you to notice me."

"How can I not? You're always around, snooping, getting into my business. You're impossible to ignore!"

"I don't mean like that." Her voice had dropped lower. If he had pearls, he would be clutching them tightly. That would have looked as ridiculous as Longbottom's Boggart, and that was quite enough to live down in the staff room, thank you very much.

It wasn't that he had been particularly virtuous, but Granger should have been running in the other direction. Far, far away. Right then would have been a good time, in fact. Instead she crouched there, staring at him. He wiggled his newly-appeared toes to distract himself a moment more. To give her time to leave.

"You should leave, Granger."

"Tell me you don't like me, then I'll leave."

"You're irritating," he said flatly.

"That's not the same thing."

"It should be taken as such."

"Tell me you don't want me."

"You should leave," he repeated.

She moved an inch closer instead. He was fucked. Or she would be, rather. Salazar.

"Fuck," he accidentally swore aloud.

"If you'd like." She undid the ties of the robe and let it slowly fall open. "Though we should probably go somewhere less damp."

"This isn't a very good idea. In fact, it's very unprofessional."

"I've been wanting this for a while, Severus," she purred.

She had him at such a disadvantage. He had refused to allow himself to think of her in this way all year, though it had been fairly tempting a time or two. Admittedly in the beginning he might have felt encroached upon, but after a time, he had begun looking forward to her company. He had possibly even grown to like her. She was intelligent, witty, and brought with her a certain liveliness that he had never possessed. But he knew that she was not for him if for no other reason than that she was young, beautiful, and had her whole life ahead of her. And so he'd shut her out, remained the grumpy bastard of the dungeons, and tried his level best to discourage her from spending too much time with him.

"You can't have," he said weakly. Of all the times for words to fail him, why did it have to be now?

"You can say yes or no, but you can't tell me how to feel about you."

"And if I say no?"

"I'll never bring it up again."

"And if I say yes?"

"Then you and I are going to go somewhere comfortable and I'm going to take off this robe and you're going to ditch the towel." She stood suddenly and wrapped the robe around her person again. He wanted to ask her to stay, but he was terrified.

"You should leave, Granger."

"You've said that three times now. Is that because it's what you want or what you think I should want? Because I think I've been perfectly clear."

"I'm too old for you."

"We're both adults."

"You're young, beautiful…" he began, listing aloud what he'd thought just moments before.

"You think I'm beautiful?" she whispered.

"I have eyes, don't I?"

She rolled hers. "Not everyone would agree with you."

"Beauty is in the eye of the beholder," he spouted. Could he possibly be more cliché? Just being around her was making his brain fuzzy.

"Do you want me?" she asked once more.

"Yes," he admitted at last.

"Thank Godric." She sighed and began untying the robe.

"Stop," he ordered. He rose to his feet, towel still held to his front. "Follow me."

He grabbed her hand and gently led her to his bedroom which was immediately illumined by the candles scattered around. He spun to face her once they were near his bed.

"May I?" he inquired, taking the ends of the ties to the robe in one hand.

She nodded, pulling her bottom lip between her teeth. She looked terribly cute whenever she did that.

He pulled open the ties and peeled back the robe, letting it fall to the floor. This time he allowed himself to look with impunity.

She radiated life and passion, all wild curls and soft curves. She had other scars besides the one from Dolohov — ones he knew nothing about, others that had been mentioned in passing — but he, too, had scars. There was nothing shameful about it. It was proof the two of them had survived.

Her warm hands pressed against his skin and, he had never felt anything so soothing. Leaning in, his lips brushing against hers. Her pliant mouth moved effortlessly against his and his towel was quickly abandoned to the delight of them both.

Skin on skin, a tangle of limbs and tongue in his bed, mussing the soft sheets and threatening to pull them from the mattress altogether. All pretence was forgotten beneath their feverish exploration of one another, punctuated by sounds only pleasure could bring forth. By the time they came together, he had already watched her fall apart twice.

"Let go for me one more time, little lioness," he cajoled. Her knees were hooked over his arms now and one of his pillows was tucked beneath her. He would cherish that pillow forever now.

"Severus!" she cried out as she reached her peak.

He had lied to her earlier. He loved hearing his name fall from her lips. Especially now. As he chased his own release, he studied her carefully in the flickering light: her eyes blown, her tongue darting across her swollen lips, skin flushed.

"Any regrets?" he murmured several minutes later. He hovered over her, trailing kisses from her forehead to her lips.

"None at all," she replied. "You?"

"Only that it was ultimately Peeves's fault."

She giggled quietly.

"I suppose even he has his uses."

He hummed and curled up next to her, warm and tired.

When he opened his eyes again, she was still snuggled into him. Squinting in the gloom, he could see that it was half six. They had indeed missed dinner. His body, however, was clearly interested in things other than dinner, judging from the way it was reacting. He raked his fingertips over her soft skin. She stirred, wiggling her bottom against him. A low groan escaped his throat.

"Severus?" she breathed.

The way she said his name made his breath hitch.

"Hmm?"

"Have you ever, you know, as a merman?"

"Was that really your waking thought?" He chuckled.

"Maybe," came the coy reply.

She had definitely thought of it earlier. Who knew she was so… adventurous?

"No, I have not," he replied.

She was silent at that, though she wiggled against him again.

"And do you think…?" She refused to finish the sentence, but from the way she pushed her bottom against him again he knew what she was after. Knowing her, she'd attempt to claim it was for research purposes. He knew better now.

"Not tonight, Granger," he said with a smirk, grasping her thigh and hooking it up over his.

"Shouldn't you call me Hermione now?" Her little laugh quickly turned to a gasp as he gave her nipple a gentle pinch.

"Don't you think people would get suspicious?"

"I'm your new research assistant," she quipped.

"Only if you wish to be," he murmured, his hand drifting lower across her belly.

"I never thought you'd ask. Of course I would!"

He chuckled against her. "It was your idea."

"So was this. So wouldn't you say I'm full of good ideas?"

"Sometimes, Hermione," he whispered low in her ear. "But right now I want you full of something else."

A/N: Hope you enjoyed this little tale about tails. Thanks for reading!