My favourite fish
mer!Robert x fem!reader
Note: Apparently I can only write about fish. So… Mer!Robert Robertson for my lovely friends from Freaktor Nation. (@hivemuthur I'm looking at you : D) There isn’t a massive build up and I think I changed who she is to him about three times, but kept it vague so you can imagine whatever c:
Warnings: Slight pantyhose fetish? Fingering (merman), oral f!, weird anatomy, monster fucking, double P in V, unprotected monster smut (wrap it up)
Word Count: 4,2k
There were a few things everyone could agree on.
One: Robert Robertson was one unlucky son of a Mecha Man.
Two: he was hopelessly, irrevocably in love with you.
One could argue that, oh, he hid it so well no one but him knew — but he wasn’t that smooth. And he had told you himself. Oh God, and you — regrettably — because you were going through a nasty breakup at the time — told him no.
Then stuff happened. Many months of not speaking, just awkwardly passing each other in the break room (always at the door: you first, no you). Many months of you trying, maybe, to fix it back into the friendship it once was… until that happened.
And since then, it had been the last thing on anyone’s mind. Especially his.
And again, everyone could agree: Robertson was one unlucky bastard.
And that unlucky bastard got caught in a superbeing’s crossfire and got very, very unluckily turned into a fucking merman.
The tank was cold. At least, it felt that way when the water wasn’t bubbling at lava-level hot. The jets had given up or clogged — he wasn’t sure — and he was waiting for someone to be sent to fix them. What he was sure of was that it had been months, and they still had no solution besides constantly probing and testing him for any possible fix. And yeah, fine, it was good they were doing that — he had to grow some fucking legs back or he was going to lose his mind — but even though the tank was big and Chase had brought him his setup, his hands were clawed now, so large he could barely press any of the buttons.
He felt — no, he was — useless. Just a little more than usual, but the feeling wasn’t new. He couldn’t relax, and he couldn’t work, and the longer he stayed like this, the more his thoughts started to drift into things like my tail is itching to stretch in the sea or I would absolutely destroy a salmon right now or — worst of all, most recently — I’d grab your leg and pull you under the water and see how you’d taste.
Fuck.
Not in a cannibalistic way — he wasn’t that far gone, he hoped — but in an animal, let me-devour-you way. Which was… great. Yeah. He’d had thoughts like this before. They were just dialed up now to an absurd level of craving. When he still had hope that the two of you could be something, he’d let himself imagine it — you in a chair in the break room, bent over a book, and him under the desk, devouring you while you tried to keep your fingers from shaking and your voice from giving you away to anyone in the nearby rooms.
And, yeah — fuck — he was hard again.
Peachy.
How many times had that been in the past few days? He’d lost count, but he was pretty sure it was the reason the jets kept clogging. And yes, he knew how gross that sounded, but his body — this new body — was dragging him through some kind of second puberty, and he was officially done with it.
His tail snapped, sending water sloshing over the edge of the pool and splashing across the tiled floor.
No matter how much he tried — shaming himself into behaving because he was terrified SDN might be monitoring him — he couldn’t stop. This was probably how Beef had felt when he’d given him that cow plushie from you and— no. He would not think about how his dog had humped that poor thing into shreds. Nope. He was better than his dog.
…Or maybe not, because the air vents brought a whiff his way and he knew — fucking smelled it through his gills — that you were in the building.
Soon the double doors slid open and you walked in, bringing that maddening scent with you. The worst part was that it wasn’t perfume. It was just you. He wasn’t a poet; he didn’t know if you smelled like caramelized apples or lavender soap. He only knew it smelled good, and it made him swim to the edge of the tank and try to hide his lower — shameful, not just because-of-the-tail — half.
Click, clack. Your shoes on the tile.
I mean, realistically, he wasn’t entirely unhappy about the whole fish situation. After all… he’d grown a second cock. So. Bonus, if you asked him. He’d never been ashamed before —just packing average — and in his rare, awkward encounters, nobody had complained. Or at least he’d never stuck around long enough to hear it. Soo… yeah. Anyway, he got two dicks now. Kind of cool, actually.
“Robert?”
Your voice. Fuck him. Had the tone changed, or was that just the wrecked fish hormones he’d been blasted with?
“Uh—” He cleared his throat. “Yeah?” Hoarse.
“Hi.” You carefully threaded your way over the puddle he’d made.
You were wearing a pencil skirt. A pencil skirt. For the love of everything he didn’t believe in, why would you do this to him?
“Hi,” he replied, a little peeved. He was allowed to be annoyed. He deserved some leeway; he had fins and felt permanently turned on as of late.
“So… how are you feeling?” you asked, not quite looking at him.
Was he really that hideous now? Worse than before?
“Well, if you don’t count the fact that I grew a tail and developed a craving for sushi, I’m doing just… fine.” Then, after chewing on his own cheek for a moment, “How’s Beef?”
“He’s doing fine. Just missing his dad, you know. I can bring him in again, see how he reacts?” You sat on the bench and pulled out your lunch.
“Nah. After he tried to eat me, I think I’ll pass. But you’re playing him my voice messages, right?”
You smiled, staring intently into your hummus sandwich. “Yup. And he loves them. I rub his belly just right, too.”
“Oh damn. I wish someone would rub my belly when I get sad. I kind of belong to the animal kingdom now.”
“Robert,” you said in that reprimanding voice that made his stomach flip. “I told you, you’re not an animal. Just a merman-type hybrid. Or, well… a mutated being. We’re still trying to figure it out.”
The last part came out softer as you took a bite of your bread. There was a crumb on your chin. His body swam a little closer on its own.
“You know you don’t have to take pity on me. I’m managing.”
He reached out with one finned hand and you slid him a peanut-butter sandwich, crusts cut off, perfect triangle. It got harder to digest every time, but he didn’t have the heart to tell you. Don’t feed bread to the fish, a silly thought popped into his head. Would they put up a sign next to the tank if he never got to turn back?
“I’m not taking pity,” you said. “Just keeping you company… it’s… well—”
“It’s not your fault. It’s mine. I went there. I intervened, knowing that I don’t— that I’m useless in the field. It’s not on you.”
You pressed your lips into a tight line, and he wanted to reach out and pull the corners back up with his claws.
“Seriously. Stop.”
“You are not useless. Without you we’re just a bunch of weirdos running around in circles.”
He hummed.
“Well, can’t argue with the weirdos part.” You splashed him, soaking his sandwich.
“Hey! My PB&J. That was below-the-belt stuff. And I would know—I don’t wear belts anymore.”
He swore he could feel your laughter in the very tips of his blue fins. They trembled when he laughed back and splashed you in return, wetting your tights. They were thin, but they were there, and he wondered how easily they would tear under his grip.
“Water under the bridge, I yield, I yield!” you squeaked, but he didn’t stop, wrapping his hand around your ankle.
He’d grown so much. Fuck. He could crush you.
He released you instantly.
You noticed, of course—you always did—and without saying anything, you slipped off your skirt, folded it neatly on the bench, and sat at the edge of the pool, legs—still in tights—dangling in the water, the black lace of your panties visible.
His cheeks burned.
“What are you doing?” His voice came out quieter, lower.
He avoided looking at you—at the way the cotton soaked up water from the tiles, at the fact that you’d have to go home commando, and—fuck. Not again. What was he, sixteen?
“Well, I figured since you don’t wear pants, it’s not a problem.”
“I have a tail.”
Your slow kicks sent ripples through the water, brushing over his scales, feeling too much like your hands—touching, smoothing over his torso, his tail, his—
“So? Still no pants. Or I could make you some. A single pant? A sock?” Your voice went up on held laughter.
That did it.
He grabbed both your feet and yanked you in.
You yelped but managed to hold your breath before your head went under. You thrashed for a second before surfacing, spitting water straight in his face—and… yeah. He liked it.
“You asshole! I have to go back after the break!”
“No you don’t. Say I had an emergency.” He stretched and swam away, careful to stay below the waterline. “What kind of emergency would guarantee I don’t get fired?”
“The water jets are stuck. I dunno. You’ll figure something out.”
“Jerk.”
“Mmm, talk to me like that more—it just turns me right on.”
“Ew, Robert.”
“Ew to you too.”
He tried not to grin, but a smile crept over his face anyway. He missed this—the banter, the jokes, even the after hours talking over the comms before calling it a day. He’d ruined it when he couldn’t keep his mouth shut and just—
The smile faded.
“So… the jets. Are they actually broken?”
His fins drooped. “Yeah. Clogged. I think it’s algae or something, but the brush is outside and I’m not rolling over there.”
You didn’t seem to notice the shift in his tone. “Why not? I could rub your belly then,” you said, snorting—and somehow, just like that, the mood lifted again.
What you did to him was more magic than growing a fish tail.
“Ha. Ha. Very funny, you.”
“I know. I’m funny like that, me” you said matter-of-factly, already moving to grab the brush.
He shamelessly watched you—the way the wet fabric clung to your hips, to your ass, how the white blouse turned translucent, revealing just a hint of what lay beneath.
His tail trembled, the tips tinting yellow.
He flexed his webbed hand a few times, unclenched his jaw, and quickly looked away when you turned back toward him.
Your jump into the pool was smooth.
“The water is like a hot tub. How can you stand this?”
“Mutated human–fish hybrid, remember? Apparently my fish parts like it toasty.” He followed you, barely flicking his tail to keep up.
“That makes no sense,” you said, frowning.
“I think growing a tail makes no sense, but hey—”
You reached the jets, thick with green sludge, and he stopped you, his face flushing red again.
Like hell he was letting you clean that.
“Here. Let me.” He gently took the brush from your hand so you wouldn’t startle. His fins shifted from pale blue to flashing yellow when your fingers brushed, and he really hoped you wouldn’t ask why.
“Are you toxic?” Of course you did.
“It’s dangerous—” But…
“What, really?”
“I’m loving it.” He had an idea.
“What?”
“Do you feel me now?”
“I sure hope not?” You swam away from him and the jets.
“It’s in the air, and it’s all around.” He scrubbed, tongue poking out in concentration, watching your confused expression from the corner of his eye.
“What the fuck are you on about?”
Then it clicked.
“You didn’t just fucking quote Britney Spears to me.”
He set the brush on the edge of the pool and smirked. God, he’d missed you.
“You’re toxic, I’m slipping under.” He didn’t sing it—just said the lyrics flatly before sinking beneath the surface, swallowed by bubbles as the jets kicked back on.
“Rob? Robert. Hey—”
You spun around, searching for blue and yellow. The tank was meant for training water-adjacent heroes, deep enough that you couldn’t see the bottom. Perfect for temporarily housing a merman—not so perfect when that merman was feeling playful.
“Robert, I swear, if you pull me under again I will go to Blazer and—”
He burst up in front of you, splashing water everywhere. He was so close. A closeness he’d never allowed himself before, but your gravity was too strong, pulling him right into your space—close enough to feel your breath against his wet skin as it cooled. He could see your chest rise and fall with borrowed gulps of air. Were you scared of him? He was more scared of you. Surely you had to realize that.
He followed your gaze with an amused lift of his brow as he watched you take him in. This—this he could get used to. You looking at him like you wanted him, like you wanted to touch the scars he’d told you about and the ones he was too embarrassed to mention. Your eyes snapped up when you realized he was watching. Gotcha.
“You will what?” he asked, using that low voice—the one he once thought you liked. His tired voice, low enough to make it sizzle. He couldn’t stop himself from drifting closer, so he could feel the water move around your hands. His tail was almost fully yellow now, stripes spreading over the blue, turning him into more monster than man.
You’d rejected the man once—he knew that. But the pull he felt now was stronger than his embarrassment, strong enough to make him hope that even if the man wasn’t enough, the monster might be.
“It’s been a while,” you croaked.
His eyes flicked to your lips, then back to your eyes. Robert made a sound somewhere between a Hmm and Yhymm. He couldn’t decide if he wanted you to keep looking at him like that or to look away before you saw something frightening and ran, realizing who you were in the water with.
“Swimmin’?” he offered, a way out.
“No, Rob.” You were tired—he could see it—so he guided you back to the edge, resting his chin on his hand while you gathered your thoughts. “Talking to you like that. Joking.”
“Ah. That. Yeah… I guess it has been a while.” He watched how your wet hair clung to your skin, how droplets gathered beneath your lips, ready to fall, and he had the sudden, sharp urge to lick them.
“And I’m sorry.” You didn’t move away from him. If anything, you drifted closer.
“About rejecting you.”
His stomach dropped. Oh. That.
“We don’t have to talk about that again,” Please.
“What I mean is… I regret it.”
There it was.
Wait—what?
He blinked a few times, trying to process it. You didn’t mean that—surely you didn’t. But then you looked at him like that, lashes low and beaded with water, eyes blown wide into two dark holes ready to swallow him whole. He let the man take a back seat and leaned into the wanting, leaned into you.
He stopped only long enough to give you a chance to pull away—then closed that ridiculous distance.
Your lips met, soft and wet and hesitant. Like lovers driving for the first time, clutch pressed too hard, stalling the engine. First kisses were often like that, but then the part of him that had mutated, the part that had put him in this tank, took over—and then let go. Let go of the clutch, let go of all restraint, free-diving when you moaned into his mouth and he was a goner.
His tail flexed, pushing you against the hard edge of the pool, claws poking tiny holes in your soaked blouse. Marble and silk, your body giving under his grip like soft clay instead of muscle. Your tongue slipped in, and he hummed , letting it happen. His other hand slid behind your ear, cradling your jaw, nudging the hinge open—open more for him. Open it all, if you let him. He wanted to taste you from the inside out, then put you back together again. He could be good like that. He could be good for you. He could be bad too, if you wanted—but please, please want him, because he’d had enough, and growing a tail hadn’t grown his patience bigger.
Your gasps broke into syllables that shaped his name.
Ro—b.
And he was do—ne.
“Please tell me you want it,” he managed, looking into your eyes—asking, pleading even, but ready to pull away. He would shove the beast back into its cage, lock his heart in there with it, if you told him to. He would starve them both with a single no.
“Yes,” you breathed into his mouth instead, and you looked—really looked—at him. Pretty. Flushed. His.
Your aching, swollen lips crashed into his again. He bit them, then your neck, nibbling until you changed color just like him. If he didn’t know better, he would have thought he’d turned into a vampire instead of a merman.
There was no one guiding it now, no one taking control. Even if he let his body decide the shape of its need, he would let you do anything to him if you kept kissing him like that. Melting—it felt like melting together, those searing, open-mouthed kisses. Your hands smoothed over him, down the sparse hair on his torso, pads soft but firm, kneading flesh, tingling where you were already mapping him. He wanted to be explored. He wanted you to claim him, plant your flag and drive it in if you wished—open him, split him, please, just do. Keep doing whatever it was that made his brain stop keeping up, leaving only feeling.
A rhythm formed: give and take, bodies pushing and pulling. Your hands found the slit where the scales hid what he hoped would surprise you.
Maybe he should wait until he was back to normal. Maybe it was selfish to want to see the look on your face. But part of him craved it—imagined the shock, feasted on the image of you discovering what he was hiding.
A cheap move, maybe. You might be disappointed when he turned back, but there might not be an after. There might only be now. And now your hand was tracing the opening where his cocks hid, and whatever arguments still floated in his head popped like a bubble.
“Keep going — you won’t be disappointed.”
He aimed for cocky and got breathy instead.
You laughed, that single puff-of-air kind of laugh. He could melt right there.
You teased him, fingers curling as you searched.
“I’m sure I won’t, Rob.” A slow kiss brushed his neck. Another followed, lingering, deliberate. You played him like he should be afraid to be in the water with you.
You opened him, spread him, held him there instead of just teasing. Like you knew exactly what you were doing. You indulged in the fantasy he’d never been able to name — the one where you took control the way he’d imagined doing to you.
Then you bit his earlobe and whispered sweetly,
“How do you want me?”
His fins shook in reply.
Replay. Over and rewind. Never returning that cassette. A sound to save for later — if later never came.
“Slow,” he rasped, begging for mercy. He had to make this moment last longer than five minutes.
Water splashed as he lifted you to the edge of the pool, guiding your legs apart with his arms. His claws caught the fabric of your shirt, slicing it. A nip at your collarbone. Your fingers tangled in his hair.
His wet body slid down against yours — wet, everything wet — and you were waiting for him as he shifted closer, pressing, squeezing, kneading. His tail rolled forward. Your tights slid against his scales: a teasing pause, slick nylon stretched thin, ready to snap but holding — a quiet, fuck-you if he knew one.
His teeth scraped your hip — a warning, a question he wasn’t even sure how to ask anymore.
But you pulled him down.
Down boy — yes, there.
So he listened, because you asked him to be good. And he chose to be.
“Fuck it—”
He bit into the inside of your tights, tugged, sharp teeth catching and ripping.
You opened beautifully.
A hole made in the fabric, just big enough to show what he was trying to see. There was no time to slide anything down — just to the side, and in, and in. His tongue — longer now, less human, more — just more — silky ribbon learning your contours by sounds only. You yelped when he pushed it inside of you, curling, searching. He wanted to do a good job so you’d keep him for later. Monster or man, just say it — he would stay like this for you.
You were sparing with words, letting your hands do the talking instead, guiding him, moving him until he got it just the way you liked it. A hitch in your voice told him he was doing it right. He looked up at you through his lashes, eyes watered down to drunk mush.
Is that good? they asked.
Yes, your body answered.
Yes. Yes, yes.
But you wouldn’t take what you wanted if you had to take it alone. You pulled him back up, kissed yourself off him, and drew him close with your legs.
His cocks were out, but poor you— you didn’t see the other one yet, letting him grind over you, coating him.
“Take what you need.” He would let you see for yourself.
So you did. And fuck — radio static skittered across his skin, hairs standing, prickling as you took him inch by inch until your body accommodated him, shaped itself around him. He moved, and you moved with him. Another slow roll, his tail working to keep him afloat as he hunched over you, gills sealing shut while his lungs took over.
“Rob—”
Moans exchanged into mouths, kisses turning into consumption. A beast, maybe — he would eat you if you let him. A rhythm formed, your fingers scratching his back as he let you guide him, let you set the pace, speeding up, slowing down, trying to get you there again — if he could at all, because fuck, he was already so close, but he didn’t want to ruin it, didn’t want you to be disappointed, didn’t want to—
“Look at me.”
Your eyes had been shut, lost in it. They opened.
Yeah. Like that baby.
He reached down, adjusted your leg, pressing the tip of his second cock into you. And there it was — that look, the one he’d been fishing for.
Surprise.
He wanted to say something, but your grin turned impish instead, where he pressed it further. Fuck. He swore you weren’t like this — though he wasn’t complaining. And you breathed something like, Yes. Please. Rob. But his mind was gone now, doing things he’d only imagined since he’d taken this form.
You’d learned one shape — but would you learn another?
The slide was slow: all out, then back in, both of his cocks inside you now, fuck — tight — your voice hitching as his did, inch by inch, slower. Your brows pinched from concentration, blunt fingers pressed into his forearms. Then he rolled back against the edge, lying down — open, ready, spread for your taking. And you did.
You weren’t in a rush — slow, circular rolls of your hips, shallow grinding instead of rise and fall, but it was enough. Your body tensed, and he watched — he watched because if he let his need take over, he would be done for. He held himself for you, stayed still for you, moaned for you, whimpered when his body protested, not happy to hold more, but you weren’t quite finished yet — not—
Then you were.
Like an arrow released, he finally let himself move, let himself thrust up, fucked you through it, wring it dry until you had enough, until his abdomen tightened and he twitched inside you — and fuck, you rode it out of him right there, every last bit, an exchange, dry for wet, until both of you were slick and dripping down his tail and onto the tile.
Your body sagged over his, and he stared up at the ceiling, dumbfounded, one arm around you, breathing hard. A pause.
“You there with me, Rob?” A kiss to his jaw — his stubble must have been itchy, but you didn’t seem to mind.
“Yeah. Just thinking—”
“About?”
“How you just fucked a merman on work premises.”
“Robert, I swear—”