Work Header

C. sapiens

Chapter Text

John is young when he’s first told not to swim too far. “The sea is deep and dark,” they say, and that does it.

He comes back three days later, his feet coral-scratched and two of his tentacles covered in stinging polyps, but he’s lit up with discovery, radiating wonder, deaf to concerned lectures.


John is not quite grown, but about to be, when he makes it to shore for the first time. It’s a seven day trek, and the water near land is far from ideal – but the world beyond the waves is new, different, tempting. When his tentacles’ efforts at locomotion become useless, John discovers the true strength of his legs, marvels at the simple elegance of feet as they carry him over dry sand.

The sun is hot and thirsty, the air is pungent with the smell of soil and plant growth, and in the distance, coming closer, John can hear laughter. John watches the humans from a nearby tide pool, sees them run and play, unencumbered by tentacles, unbothered by the sun, unfettered by the water.

When he returns home, the elders warn him not to go back, not to let the sun take his water, but their words only serve to pull his thoughts into this new and tantalizing stream, an irresistible current of want.


“Please reconsider,” they say as John prepares to leave, says heart-felt goodbyes, tearful ones, painful ones, but says them nonetheless, “– it’s a great wide world out there –”

Exactly, John doesn’t say. They won’t understand.

“ –Full of danger –”

Perfect. John flashes a grin through his goodbyes. He’s old enough to leave and doing so, thank you very much.

“ – all sorts of danger,” his family and elders say, desperate to put him off. It’s one of the many marks of their failure to know him that they think this will dissuade him. “These feelings will settle,” they say, and, “You belong here.”

John doesn’t bother shaking his head or telling them they don’t understand. He simply turns and leaves. Danger is a bright light that draws minnows to the sharp-toothed dark, and John has always wanted to bite back.


It’s incorrect to say John lets the sun take his water – rather, he gives it willingly on a shore near what he learns is a city called London. He goes on to learn a great many things in that city, too, but its name is the first thing he learns on land, and he always holds it close. Later John joins the army, sees the great wide world, and gets shot for his trouble. John nearly dies in the most statistically unlikely place for his kind.

Blood seeps into sand, onto hands, into bandages, and John bleeds into fever. When the dry heat breaks, John limps back to London – close enough to smell home, but refusing to properly return. Not that he could even if he wanted to – not with his water gone.

And besides, not long after, John meets Sherlock.


Danger was not the only card played in a bid to keep John from the land. His parents took him aside before he left and asked a serious question, a worried question: “And what of your Tide? If it comes for you, what then?”

But John only shook his head. Where the others of his age were feeling a pull towards one another and waking to the writhe and want of tentacles, he felt only an itch. It made his legs twitch in his sleep, made his toes curl into the softness of the sea bed. It made him ask forbidden questions, like: Why do we have feet? Where do they come from? Where do we come from? It earned him many lectures and stern silences.

Still, John felt a frisson of trepidation at the thought: What if I am in the wrong place when my Tide finally comes?

But it doesn’t. For years it doesn’t. John runs and fights and bleeds and almost dies, and still it doesn’t come.

It doesn’t, and it doesn’t, and it doesn’t for so long that when it finally does, John mistakes it for something entirely different, for friendship (because Sherlock and he are friends now – right?); the most unlikely of flatmates (even without adding in John’s origins and original physiology) solving cases and saving each other in countless grand and miniscule ways, spending their days together, together, together. Sherlock, daft git that he is, runs, and John follows, straight into danger, into all sorts of fire, and John feels he is alive and thriving and bursting with joy, present in a way he’s never felt before.

And besides, John had given up expecting to ever feel this way years ago, so there’s no reason to pay any attention to the signs at first.

But confusing and overlooking the indicators doesn’t change the fact that John’s Tide, decades late, finally arrives. It sneaks across his body like the neap swell it isn’t, and when John finally sees it for what it is, a spring tide and most definitely proxigean, well, by then it is too late.

The want creeps in slowly, inexorably, soaking into his skin like wavelets into too-long dry sand, and if asked what day the Tide turned and began its advance, John would be hard pressed to answer.

He honestly doesn’t know how he got from running after Sherlock to looking after Sherlock to lusting after Sherlock – although ‘lust’ is one of those empty land words that falls short of what he wants to say, falls weak of what he actually feels.

It develops slowly, develops deeply, and John struggles with it, with this new pull, because it’s impossible and he can’t expect Sherlock to understand or even sympathise. He tries to hide this new facet of himself as best he can, but he knows his behavioural patterns shift, knows it’s only a matter of time before Sherlock notices.

It never even occurs to him to leave.


It takes Sherlock quite a while to go from not seeing and not seeing and not seeing to suddenly seeing – but then again all of Sherlock’s breakthroughs seems sudden in their brilliance. After all, it must have taken quite a bit of adjusting and tinkering with his ‘improbability vs. impossibility’ world view along the way, but the fact remains: he settles on an answer, and then he comes to John with it.

John is having breakfast when Sherlock confronts him.

“A few weeks ago I would have thought you were impossible,” Sherlock begins, walking into the kitchen in his blue robe, and John – not quite catching on – wants to scoff and argue, No, actually, you are impossible, but then Sherlock continues: “But now I’d say you are improbable.”

John thinks this might be flattering, if he could wrap his head around it, but he can’t – Sherlock is standing near, steaming his sun-baked-clean-sand smell, like the beach after rain, an alive smell, an other smell. It’s intoxicating, and John has been studiously avoiding it, but he can’t shift away now it’s so near. Now Sherlock’s so near.

And then Sherlock ruins the probable-loveliness of his words and the definite-beauty of his presence by saying: “And by ‘improbable’ I mean ‘not yet scientifically acknowledged.’”

John blinks.

“Ah,” John says, suddenly a whole lot more present. He shakes his head to try and clear it, but all the air around him is imbued with Sherlock, and well… “Ah,” he says again, after other, more useful sounds fail to present themselves for vocalization. He adds, “Um,” to the list of contributions he’s made in effort of keeping his secret a – well – secret.

Sherlock rolls his eyes and moves away to rearrange his mad scientist set on the table. “You needn’t bother denying it, John, you know my methods. And furthermore, you needn’t bother worrying so – I’ve known for a few days now and have yet to alert the National Science Academy or Baskerville or even my dear brother.” John is just compos mentis enough to hear the crowing in Sherlock’s voice over keeping Mycroft in the dark. Meanwhile, Sherlock continues: “So unless your natural heart rate is only now presenting itself, you may wish to calm down, as I can see your pulse fairly thrashing in your throat. Tell me, do you have gills?”

“Oh,” John says faintly. He takes a deep breath – and then another when he sees Sherlock staring unblinkingly at him as he does so. “Er – no, at least, not where you can see them.”

Sherlock’s eyes light up, delighted, and John thinks for a moment, I should’ve told him ages ago, if I’d known he would look at that.

“How?” Sherlock asks, breathless, and John wants to put the breath back in him just so he can take it away again. “How – how are you? And why? And –”

John gets up, fetches a cup of water, drinks it down in a few swallows. He pulls stale oxygen from the water, but it soothes his aching gills even as the water pools in his belly and cools him, just a bit. He feels calmer, but also knows his hand won’t tremble now.

Danger of all sorts, indeed, he remembers.

“I don’t have any answers,” John says, then forestalls Sherlock’s outrage at being denied answers by lifting a hand and adding: “The elders never answered my questions.” John pulls his mouth sideways to show he’s just as displeased.

Sherlock shuts his mouth with a click, lifts his hands to his chin, and after a moment’s thought asks, “Why are you here, then? And why do you look so –”

“Human?” John offers.

“Unremarkable, I would have said, but yes, let’s go with ‘human’.”

“Prat,” John says, feeling just a bit unbalanced by their easy banter and familiar teasing – shouldn’t there be shouting or something?

Sherlock smirks at him, and John snorts, considering his answer.

“It’s called ‘trading,’” he says at last, “but it just means letting go of your water – your home water,” he clarifies. “That’s when you let the sun and the land and the wind bake it away. It distills you into human form, and it means you can’t ever really go home – but then again when I did it, I never thought I’d want to go home. Still don’t. Never felt like much of a home, anyway.” He tries for a smile, feels its ache, and stops trying. “Oh, and you can forget about me showing you my other form, first off because you’d only want to take samples, and second because I can’t, it won’t work without my home water. So you can put those big eyes and pouting lip away, don’t bother.”

“Afghanistan?” Sherlock asks after an eye roll that erases the pleading from his face as if it hadn’t been there, a brazen bid at manipulation.

John purses his lips. “A way to see the world – and to get some excitement at last. Current events weren’t all that thrilling.”

Sherlock favours him with a blank expression.

John snorts out a chuckle and feels more himself as he says, “That was a joke, Sherlock. Current events? Oh, never mind.”

Sherlock frowns at John, and it turns absentminded halfway through. Then he ups and asks what, in John’s opinion, is the most dangerous question: “We’ve lived together for quite some time now. Why did I never notice before?”

“Ah,” John says, master at delicate answers that he is. “Um.”

John,” Sherlock says, and there’s a note of warning and eye-rolling impatience and pleading in there all at once.

In answer, John blushes. “It’s – it’s –oh hell, it’s called the Tide. And um, it comes for everyone? Although I didn’t actually think it could happen without home water.” He bites a lip. He hadn’t thought it would happen to him at all, home water or no. “And now it has?” God, and at his age – how? How?

“What is ‘the Tide’? What does that mean?”

“It’s – it’s… a response to environmental stimulus.” He won’t meet Sherlock’s eyes, only hopes that Sherlock assumes it’s something other than the urge it actually is. “Don’t worry, it’ll run its course and then it’ll be done.” Hopefully.

Sherlock is quiet for a long few moments, lips pinched, eyes narrowed. At last he says, “Does this change anything?”


Sherlock looks frustrated and somehow pained as he clarifies: “Will you…be leaving?”

John’s mouth falls open. “No?” he ventures. “I wasn’t planning on it – oh, god, do you want me to?” The thought that Sherlock might not want him to stay after he found out hooks into John’s chest and twists.

“No!” Sherlock answers, an over-quick bark of an answer. He visibly reins himself in. “No, I – I just. No.” He shifts his weight from foot to foot a bit before he says, “This is your home as much as mine, and therefor the phrase ‘you are welcome here’ is a bad fit, but –”

“You don’t want me to leave, then?”

Sherlock takes a quick breath. “I want you not to leave.”

John blinks at that. It’s – it’s a very un-Sherlock way of saying the thing, and if he weren’t exhausted and a bit off-kilter, he might’ve been able to make sense of it, but instead of clarity his head is filled with murk. “So you – you don’t mind? Me? This?” John gestures at his body, at himself.

“Don’t be an idiot, John,” Sherlock scoffs, then turns and fiddles with something on the counter behind him. “Of course I don’t ‘mind,’” he says, and it’s low and not at all as brash as John would have expected.

“Alright, then,” John says, because those words are (almost) always (mostly) safe. “That’s – that’s good.”

Shortly thereafter Sherlock receives a text and dashes out, and John goes for a walk, needing the air he chose.


It isn’t until later that evening, when John is having a cup of tea while he reads and Sherlock is sprawled on the sofa, laptop open on his chest, bathing his face in white light, that they speak again. Sherlock hadn’t texted since their morning chat, and John hadn’t wanted to intrude, still feeling a bit uncertain of this new knowledge between them, this new sharing.

It isn’t until Sherlock speaks that John knows everything will be fine, though, because the daft sod opens his mouth and says, without looking away from his screen:

“John, your current events joke was appalling.

John nearly spills his tea laughing, and Sherlock goes from looking baffled to bemused, one or two illicit chuckles escaping the confines of his chest and shaking his laptop, making the light on his face dance, and it feels like John can breathe again.


The Tide keeps rolling in, bringing with it dreams of the crush of waves above and around, the gasp and surge of water through gills, the distantly-remembered thrill of powerful speed through clear seas.

John prefers these dreams to his usual – Afghanistan or Sherlock getting himself killed – but they grow in frequency and detail, begin to blend details of his days in 221B, and he wakes confused more often than not, his skin tingling, his legs shifting, as if every part of him is searching, reaching in the dark.


It’s three weeks after Sherlock’s discovery (weeks filled with chases and evenings together and Sherlock trying to see if John will avoid eating certain foods – like sushi – or prefers them, as the case may be) that John wakes from dreams of distant, dull roars, of a heaving, roiling sky, of the pull of water and a far-away weight. His back is sore, his muscles are weak, his mattress is damp.

It’s that last fact that has John jerking his eyes open and sitting upright. His arms quiver as he regards himself in shock.

The mattress is damp because John is sweating an almost obscene amount – he’s covered in a sheen of what smells like salt water but feels like slick sweat and tastes like – like – John has no clue, but it’s not bad.

Quite pleasant actually.

It is a bit sticky, however, so he gets up on wobbly legs and heads to the downstairs tub, starts the shower as he strips, gets in –

And promptly sits down hard as he goes weak at the knees. He manages to plug the drain with the stopper, wanting water, water, water lapping at his skin, wanting skin, wanting –

He blinks, blinks, and then his eyes close properly.



John wakes to the sound of water on water – rain on the surface of the sea above him – and Sherlock’s voice, the combination of which is rather nice.


Louder this time. Lovely.

John opens his mouth to say, ‘Yes?’ or ‘What?’ or even ‘Sherlock,’ because his mouth likes Sherlock’s name, holds its syllables like two smooth stones on his tongue, always ready to let them slip out.

But when John opens his mouth and tries to take breath to speak water rushes in instead, and for a moment his land-lungs panic – what the hell are we supposed to do with this?! – and then his throat gills take over with a stretch and flutter, quivering with the strong pulls of water he takes while he recovers from the surprise and the breathing mishap.

“John – John!” Sherlock’s hands plunge into the full tub and grasp John by the shoulders, and hoist him up to the surface. He breaks into the air with a wet gasp, water pouring from his mouth and nose, hands coming up to latch onto Sherlock’s wrist in an effort to stabilize himself and calm the man shaking him. “John are you – are you –”

“I’m fine,” John splutters, gasping, and his throat aches from the sudden switch, water for air, cool liquid for warm, dry gas. “Jesus, Sherlock, stop shaking me, I’m fine – must’ve dozed off.”

Sherlock lets go and John slides down a little, and Sherlock lunges forward to stop him slipping back into the water, but then flinches back. John thinks it must be that Sherlock realizes John won’t drown if he slips back under, but then he sees the shock and confusion on Sherlock’s face and finally looks down at himself.

“Oh.” That…explains a lot.

John’s body, in his sleep, in this tub, in this water, seems to be trying to remember itself. Seems to be succeeding.

Spongy tissue has lifted away from his hips in four great lengths – broad where they attach (two above his sacral dimples and two just below his hip bones) and tapering down to thick tips. The back pair are a meter and half or so, the front ones only a meter at best. They match his skin for colour, albeit shaded brown along their centres, with suckers beginning to take shape, larger closer to his torso, growing finer towards the tips. He can see the slits at the ends of the two dorsal arms that expose pale, almost translucent flesh, delicate and water-logged. Water-hungry.

John shudders as his whole body seems to pulse, and the water level in the tub dips noticeably even as his fleshy tentacles grow a little less flimsy, filling and reshaping themselves with this new water.

“That – that explains why the bathroom isn’t flooded,” John says, a bit delirious, blinking up into the shower spray that isn’t being blocked by Sherlock. Little droplets seem to sizzle into him where they land on his new limbs. His human skin is less permeable, and the droplets roll down, tracing paths like a lover’s fingers might. He’d be worried about how impossible this all is if it didn’t feel so bloody amazing.

“John –” Sherlock breathes. “Are you alright? Does it hurt?”

John shakes his head, lets his eyes flutter shut. “No, feels good,” he says a moment later. “Like breathing. Like sleeping. Like touch.” He’s rambling, he knows, but everything feels perfect. The water around him, in him. The air in his lungs and mouth, softly abrasive. The vibrations in the room and in his throat. Everything.

“Is this part of the Tide?” Sherlock wants to know, his eyes roving over John’s new form. “You said you couldn’t access this form anymore.”

“Yes, and I don’t know how this is happening, Sherlock,” and John means to sound curt, because he doesn’t want to be answering questions right now, needs Sherlock to leave so he can try and sort this out without losing his mind – but Sherlock’s name in his mouth is a long, delicious sigh. “Shouldn’t be, shouldn’t be,” he murmurs, letting his head rock from side to side, enjoying the lapping of the little waves that causes, the wet caress of water. “You should probably leave,” he sighs after a long moment of indulgence. His body is shifting in earnest now, waking to wants water cannot sate. It’s a slow undulation, endless, and his skin turns slick, slicker, his legs and tentacles tangling sensually against one another. “It’s time now. My Tide – it’s come in for me, and –”

Response to environmental stimulus,” Sherlock mutters to himself, then his gaze snaps to John’s. “You meant sexual maturity,” Sherlock says, eyes widening with realization, but John shakes his head.

“It’s not maturity, it’s – it’s a breeding cycle,” and oh god, he can’t believe he just said that to Sherlock, and his mouth just keeps pouring out words: “Don’t know how this happened. Never happened in my home water, never thought it would happen on dry land. Should only kick in when there’s a potential mate nearby – ah –” John arches against the surge of want his body feels, a rush from head to toes and tips.

“What happens now?” Sherlock asks, and his voice is quiet, fact-gathering mode, and John huffs out a laugh.

“You leave and I – uhh – I try to take care of this – and – and then dry out again. That’s the plan, anyway.” Please let that work…

“Don’t – don’t you need a mate?” Sherlock, as always, asks the question John would rather he didn’t. “Isn’t that the point of this… situation?”

John opens his eyes to tell Sherlock to leave off and get out – and then has to stare and make sure, but yes, Sherlock is, in fact, blushing. “Are you –” John’s mouth works a bit, soundlessly, then runs away without him: “Are you volunteering?”

“I –” The blush deepens.

John groans, throws his head back. “I – I don’t know if that would even work, Sherlock. This is new for me, too. I don’t know if this –”

“What does the mate have to do?” Sherlock asks, and he’s crouching by the edge of the tub, so close, and his scent wafts over John, and he wants desperately to pull water into his throat, into his cells, that carries that smell. Sand and sun and bleached driftwood. Old bones, new water.

“Be willing,” John breathes, losing himself to the idea. “Be open.” Words from long ago fill his mouth, from elders John had discounted at the time. “Be mine.” John’s hand lifts from the water, grips the edge of the tub before finding Sherlock’s hand and clasping it. “Are you?” He trembles; even taking Sherlock’s hand feels potent, lights his palm and fingers and wrist in touch.

Sherlock returns his grip and nods.

“Say it,” John says hoarsely. “Say it, say it,” and his body thrashes with the need to hear Sherlock shape those sounds, those specific words:

“I am.”

John moans, lets slip the smooth stones of Sherlock’s name, and then Sherlock is turning off the shower and stepping into the tub, and water is sloshing everywhere, and there’s an awkward moment where they don’t seem to fit, but John’s tentacles drape over the sides, out of the way, and Sherlock kneels between John’s slightly bent legs.

“John?” he asks, sounding lost, and John sits up, struggles forward against his own new mass until he remembers he can push and pull with his new-old appendages.

John places his hands on Sherlock’ shoulders. “You – you really don’t have to do this, Sherlock.” God, Sherlock’s skin is hot to the touch, and the air around him is laden with that irresistible scent, and John hopes it’s arousal – but without the right pheromone signals, he can’t be sure.

“I know,” Sherlock breathes. He takes John’s hand from his left shoulder and brings it to his lips, kisses it, pulls his lips away wet, a little bit sticky. “What –?” he asks, turning the hand to look at it more closely.

“Its – it’s for –”

“Copulation?” Sherlock supplies, rubbing a thumb along the heel of John’s palm.

John flushes. “Yes. Makes – it – easier in water. Slick. Makes everything –”and John’s words fail and his eyes go wide as Sherlock licks the wrist he’s holding. John holds his breath as Sherlock’s eyelids flutter.

“Oh, that’s –” Sherlock’s eyes open, and he takes another taste, and John can see the flush spread down Sherlock’s throat and chest. His eyes are dark, a little unfocused. “Oh,” Sherlock breathes.

“Last chance, Sherlock,” John says, trembling from those two brief touches, from the change in Sherlock’s scent. “Please, please be sure –”

“I am,” he says, and then he lurches forward and John pulls him close, and their mouths meet, hard and hot and hungry.

Sherlock’s mouth is warm, wet, pulsing with life, bathed in air, in breaths, and John swallows them down past his gills, wants that air diffused inside, inside – and those sounds, too, while he’s at it. Sherlock’s voice is dripping out of him in little bits, high pitched and needy, with a deeper undertone, an intermittent roll of darkness that seems to resonate in John’s bones, and John can’t get enough. He wants every drop of sound, every brush of contact, every inch of skin, of Sherlock –

“Clothes,” John pulls away to say, then dives in again, letting his mouth travel where it wants: Sherlock’s lower lip, neck, ear, clavicles, and mouth again. He tastes like high tide, water claiming land, the meeting between the two a pulsing, thrashing dance.

Sherlock’s hands fumble with his buttons, take too long, and John grips and rips, buttons ping and plink into the water, and yes, yes, skin, glorious skin, pale like the ocean floor, pristine.

“John!” Sherlock probably means for it to be a complaint, a chastisement, but it whips through the air between them, a breathy whisper; it coaxes a thrum from John instead of chagrin, and now the tentacles that had been keeping them upright rush in to twine and twist and push and pull and tear, flinging scraps out of the tub, and Sherlock quivers and cries out and doesn’t resist as they both slide lower into the water. His heart is pounding so loud John can hear it, feel it, Sherlock’s breath huffing out in great gasps. In mere moments he is naked above John, naked and hard and yes, willing. “John,” he breathes, and John’s tentacles bring them together, propped so that Sherlock’s head is properly above the water, held so that there isn’t an inch of space between them anywhere. John can already taste Sherlock in the water, them in them water, and he tips back and to the side a little further, swallows down a few quick mouthfuls, shivers as that water lights a path of want from mouth to throat to belly to tentacles –

Sherlock is licking his lips as if in a daze when John’s eyes flutter open, both of them now well and truly caught in the Tide. It makes no sense – pheromones shouldn’t cross the DNA gap, and Sherlock is neither female nor fertile, has no Tide, will have no Tide, and yet –

Sherlock starts to grind against John, slowly, and for a moment John isn’t sure if perhaps his tentacles are pushing Sherlock against him, but then he feels Sherlock tense and twist to bring his hips to bear with greater pressure, and John groans from the pleasure of the touch, from the ecstasy of the thought. Willing. “Yes, yes,” John sighs and murmurs, tilting his head back, letting the feeling pour through him. “Oh – oh, Sherlock?”

“Yes? Oh –!” Sherlock finally notices that one tentacle has wound its way down to the curve of his arse. “Oh,” he breathes.


“Yes, John, I –”

“I know, I know,” John says, kisses him again, feels Sherlock tremble against him, under his tentacles’ caressing hold, suckers gently gripping and releasing, trying to calm his mate. “Slow, we’ll go slow.”

Sherlock nods, lets his eyes fall shut, leans forward in the cradle of John’s limbs to arch his back, an offering, and John cedes control to his want, lets it expand inside him like a bubble chasing the surface. John feels the shift in his dorsal tentacles’ skin as softer flesh moves forward beyond the texture of the suckers, in preparation for touching, for pushing, for giving and taking pleasure.

He is true to his word, he starts slow, lets that exploratory tentacle sneak lower along Sherlock’s cleft as they kiss and move against one another, until a hot and twitching patch of furled skin arrests his movement. They share a soft exhalation, and then Sherlock moans, because the tip of that tentacle is slick and clever, flicking slowly back and forth, like licking.

“Oh, I – ” Sherlock begins, but falters and licks his lips. He’s never looked more beautiful, more delectable, his sex flush a lovely rose, his lips kiss-drenched and bruised, his eyes almost completely pupil. “You taste – you feel – I want more,” he groans.

Pleasure is shooting up the arms of John’s tentacles; just touching Sherlock is entrancing. Feeling him respond to caresses and kisses and that one, questing tip is breath-taking, water-giving, like tasting home. “It – it’s the –” John tries to explain but cannot, struck momentarily mute as Sherlock arches against him, catching their cocks against one another and between their abdomens.

“Excretion,” Sherlock supplies with a slight hitch in his breath, and John can’t help the fondness that breaks through his want for just a moment. Sherlock in the moment, in the act, remains Sherlock nonetheless, and John gives into the warmth in his throat and chest that spills over into a grin as he watches Sherlock’s eyes try to flutter open.

“Yeah, that,” John says. “It –”

“Pheromones?” Sherlock asks. “For signal – signaling mating intent – or enticing a mate, or –?”

“Pleasure,” John sighs. “They – it means I’m willing. You –”

Sherlock’s soft moan sends thrills of pleasure along John’s skin, raising little bumps, making the three less occupied tips of his tentacles curl and twist like wriggling toes where they twine around pale limbs. “I –” Sherlock swallows. “I’m sorry I don’t have any,” Sherlock says in a rush. “For you. I am though. I am.”

John’s skin writhes with those words, sensitive and craving. “I believe you.”

“Good. I –”

“As for not having any pheromones – I beg to differ.” John lifts and pushes and takes Sherlock’s cock into his mouth in one, steady movement, drinks in his taste, his sounds, relishes the way Sherlock’s fingers seize and tangle in his hair. He pulls back, groans out, “Oh, Sherlock, amazing – want you –” and then surges forward to take him in his mouth again and again.

“Oh god,” that gorgeous mouth lets slip, and then again, and then, “John, I – I –”

John sucks and works his tongue, reveling in the musky, sea-rich taste of him, burying his nose in Sherlock’s patch of dark curls and scenting him, mapping his arousal. He feels Sherlock begin to tremble, runs the tips of his fore-tentacles up Sherlock’s torso: navel, sternum, nipples, clavicles, neck, jaw, chin –

Sherlock dips his head and captures the sensitive tip of John’s right ventral tentacle in his mouth, which is hot and wet. He begins suckling almost immediately, coaxing the tentacle deeper before John even has a moment to respond beyond gasping and arching, almost forgetting to curl his tentacle’s edges in on themselves to keep the suckers from harming Sherlock’s tongue. The hasty movement squeezes more of John’s pheromone-laden wetness out, and Sherlock groans at the sudden flood, swallows and licks and goes limp in John’s hold even as his pelvis begins to tilt towards John’s mouth, eager, urging.

John moans around Sherlock’s cock in his mouth and throat, his hands scrabble at Sherlock’s waist, grabbing and holding him, and all his muscles tense, pulling Sherlock close and further into his throat. John feels himself slip even deeper into that mouth, and Sherlock swallows against John once more, hard, and then comes with a high keen, startled, and convulses in John’s hold, in John’s mouth. His release is thick and brackish and plentiful, and John swallows, swallows, wants every last molecule of Sherlock that he can get.

He pulls back after a last few lingering licks, rubs his thumbs where he’s pressed them into Sherlock’s hips firmly, grins up at Sherlock. His mouth has gone slack, and John’s fore-tentacle slips from those lips to curl adoringly around Sherlock’s jawline and neck before draping itself over his heaving shoulders.

“Oh god John,” he pants at last, “is it – does it always feel like that?” His voice is a little soft, a little overwhelmed.

John feels a surge of feeling for the man atop him, wants him in a way he knows won’t diminish. “No,” he says after a moment. “I hear it gets better,” he growls, tips Sherlock forward and down for a kiss that starts simple and grows heated until Sherlock sits up with a groan, and stares wide-eyed and bewildered down at his own renewed erection.

“That doesn’t usually – um –”

John grins and reels Sherlock in for more kissing, tasting his slick in Sherlock’s mouth, wondering if Sherlock can taste himself in John’s mouth. “Excretion,” he teases, “pheromones,” he reminds. “God, you’re so receptive,” John groans as Sherlock whimpers, his hips starting to rock in a bid for friction once again. “I mean,” he says, retreating from the press and bite and smear of kissing, “We can stop if you want, we don’t have to – again –”

“Don’t you dare stop,” Sherlock cuts in, and his eyes are open and blazing and on John.

John snorts, and they kiss again; Sherlock has his arms tucked under John’s shoulders, pulling them close together until it is less a kiss and more a mutual bruising of lips. John pulls back after a long minute, lips tingling, and asks, “Ready?” and Sherlock nods, the curiosity in his eyes converted to arousal as John’s squirming dorsal tentacle begins smearing broad swaths of friction against Sherlock’s anus once more. Now, post orgasm, the skin there has more give, the muscles beneath less tight, and John can feel them flexing with each stroke.

Sherlock’s breathing grows harsher, loud beside John’s ear, and it almost seems far away, removed somehow, when John’s tentacle stills its undulation, stiffens as it reaches further out from the slit, and begins to push into Sherlock with tiny surges. They both groan, Sherlock’s eyes wide with surprise, John’s slitted with tightly reined pleasure.

“Oh god, Sherlock, oh god you’re so hot inside –” John breaks off in a hiss, head tilting back as he tries to parse the slew of sensations radiating up his dorsal tentacle: heat, pressure, friction, a flickering heart beat thrumming high.

Sherlock shudders, clenches ineffectually against the slippery intrusion. “You’re – ah – quite cool, actually.”

John huffs out a laugh as his tapered tentacle slips further in, contracting to squeeze out a coating of slick as it goes. “Give – give it a moment – there, oh there.”

Ah! John–!” Sherlock squirms against him, in his grip, writhes as John’s tentacle expands inside him, filling with blood and water heated by his core until it is a firm and hot presence inside Sherlock. The end of the sheath arm splays to hold Sherlock firmly by the arse, kneading his buttocks and spreading him open ever so slightly as John’s penetrating tentacle stiffens – and only then the muscled length of it begins a shunting, shoving sort of rhythm, and the result is that Sherlock keens, penetrated shallowly and in quick thrusts. “How – oh god, oh god more, oh fuck –!” Sherlock’s body rocks with each thrust, his pelvis jerking arrhythmically until John’s ventral tentacles shift to guide it in cadence and direction, pressing it firmly back into John’s advances. Sherlock makes a high pitched noise then, arms scrambling for a hold on John’s shoulders, his legs starting to shake.

“Oh, that’s it, that’s it,” John gasps. “Open, open for me –”

And Sherlock does, his muscles loosing and John finds he can slide in, and in, and in, finally extending fully into his mate – and then out again in a long, slow retreat. Every breath Sherlock takes seems to be a gasp, every exhale a shocked moan as John’s body overwhelms his with sensation, with stimulus: undiluted pleasure.

With a gasp, John surrenders to that same sensation, does what feels right, what feels needed, lets his body and limbs hold Sherlock up and at an angle, arches against him, captures lips and tongue in ravenous kisses, and lets the slide of skin and touch inside and out consume him, consume them both and then Sherlock cries out, mewling as John stiffens in an arch and comes, filling his mate with warm pumps of slick.

“Oh god, oh god, John – please, oh god –” Sherlock writhes in his hold, and John can feel that he’s close, see it in his twitching cock and quivering muscles and flushed skin.

“Shh, Sherlock, it’s okay,” John mumbles, and then he’s on his knees and Sherlock’s pressed close and hot against him, breath harsh with impending pleasure, “not done yet, not done yet.”

Sherlock groans as John’s first tentacle slips from him, pants as he’s left gaping, says, “John,” voice raw with want and an edge of uncertainty – and then John’s second dorsal tentacle surges forward, eager, taking Sherlock in one, insistent push, cool at first then flushing hot and hard, unfurling inside, and Sherlock cries out inarticulate, again and again as John takes him, claims him, fore-tentacles holding him still, holding him up, the sheath spreading him for John once more. “Oh fuck, Sherlock, oh god you’re gorgeous,” John says, cannot but say, as Sherlock’s damp curls shift with each thrust, as his plush mouth parts with his panting, and his eyes flicker with sensation, his skin painted with arousal.

“I – I – John,” Sherlock groans, words and voice slipping higher, higher – and then his whole body tenses into a bow and his inner muscles clench and clench and clench, just as John’s tentacle pulses, pulses, spills into Sherlock, but it’s not enough, he wants, he wants –

With a hoarse cry, John manages to lift and tilt Sherlock up and forward, tentacles and arms weak from a bizarre blend of orgasm and acute desire. Sherlock moans, tries to shift forward to help, but just slumps into John’s arms and fore-tentacles as John pushes up into him with his cock, replacing his spent tentacle and seating himself fully in one, smooth movement. Sherlock’s hands clench and stagger against John’s shoulders and back, a soft litany of “oh, oh – oh,” keeping time with his body’s spasms.

Drowning in Sherlock’s touch and air and sound, his land-limbs quivering, John shoves up into Sherlock one, two, three times, and then he’s coming, too – his muscles tightening, his tentacles crushing them together almost to the point of pain as he undulates against Sherlock, thrusting through his orgasm, and each pulse pushes warm liquid from Sherlock to spill into the water and onto John’s thighs and tentacles. This pleasure is more familiar, old acquaintance throughout his dry years, but he finds he needs to grab Sherlock’s hips, desperate for an anchor in this moment as his tentacles shift to try and hold them both up. John’s voice shakes as he groans out his release, and Sherlock is keening, voice almost translucent from use, as his muscles cycle through the last of the aftershocks, tightening deliciously around John – and then they are breathing together, harsh in the sudden quiet.

John loosens his hold at last, pulls out, pulls back.

“Sherlock?” Sherlock sags back into the waiting cradle of John’s fore-tentacles, and John steadies him with his hands. The water in the tub is down to a few inches, and at least two shirt buttons are digging into John’s shins where he’s somehow ended up kneeling.

“John.” His mat– Sherlock’s eyes are closed, his mouth slack, barely forming words.

John’s breathing is still harsh as he asks: “Sherlock, are you –?”

“Yes, John,” he says quietly, fervently. “I am.” His eyes flutter. He frowns slightly, shifts, and John feels a warm flush of his mixed come bathe his legs before clouding into the water, and Sherlock groans. His eyes twitch behind his lids, once or twice, and then he opens them, blinking muzzily.

“We need to get you out of the water,” John murmurs, wonders if he’s allowed to care for the man in his arms now that the Tide is receding.

“’m fine,” Sherlock mumbles, head lolling side to side.

“Yeah, right, c’mon, up we go,” John urges, deciding personal space and post-coital awkwardness can wait until Sherlock isn’t in danger of drowning – or catching cold, at the very least. John’s not long for wakefulness, either, but at least his physiology is built for the intensity of what they just shared. His tentacles are rubbery with exhaustion, drained from use, so John tucks them around Sherlock’s shoulders and hips, holding him close and upright as he stands for them both; his legs quake, but hold.

The first few steps are slippery enough that John nearly sends them both pitching sideways; he’s happy to reach the door to Sherlock’s room, happier still to reach the rug beside the bed.

“Hey, c’mon, let’s get you dry, Sherlock –”

Sherlock slips from his careful hold to flop backwards onto the bed, boneless, pliant, not quite asleep, but writhing on the edge. “Hmm, John,” he sighs, and John catches himself smiling at Sherlock, at his chest rising and falling slowly, at his left hand’s fingers curling in a twitch, and at his closed eyes and parted lips that seem to curl up just at the very edges. John’s not sure if the smile’s allowed, but Sherlock can’t see it, so maybe it’ll be alright, one way or another.

He slips from the room to grab a towel, walking carefully as his tentacles wind themselves back into their dormant places, despite being nowhere near flaccid enough to pull their disappearing act.

In the bathroom he stares at himself for all of thirty seconds, shakes his head, and then snatches up what he needs. The tub still holds their water, their shared Tide, and it takes no small amount of willpower to keep from bending over the ridge of the bath to dip his mouth and take a few, last gulps. But getting even more caught up in Sherlock isn’t going to help anyone, so John steels himself against that act.

Mouth dry, John makes do with a few sips from the tap, pulling a face at the subpar flavour (Sherlock’s arousal tasted infinitely better) and heads back the room.

Sherlock blinks open sleepy eyes as John sets about drying him, trying not to linger over the obvious erogenous zones.

“No, stop being an idiot,” he slurs, giving John a minor heart attack and making him want to smack him in short succession.

“Getting you dry so you don’t get sick is not ‘being an idiot,’” John counters when he thinks his voice will be steady.

Sherlock snorts, not lifting a finger to help. “Mean this. This,” he repeats, as if that clarifies anything.

John rolls his eyes, lets his mouth quirk into a sideways grin. Safe – or safer than the smile that threatens. “‘This?’”

“This,” Sherlock agrees. “You being this. Worried.” He scoffs, but he’s exhausted, so it emerges as more of a hiccupped sigh than an actual sound of derision.

“Well – I mean,” John begins, but then Sherlock hooks John with a leg and an arm and turns over so that John ends up sprawled half on top of Sherlock, towels and all. John makes a most dignified squawk under the circumstances, but that doesn’t have much of an effect. “Sherlock, what –”

One long, pale arm reaches out and pulls a jumbled pile of sheets and covers onto them both. “Fix them,” Sherlock commands sleepily, chin-nodding at the sheets.

“Sherlock –”

“Or are your appendages not that articulate?” He shuffles to face John as he asks, but keeps his eyes closed.

John sighs, but lets his tentacles slither out to straighten some of the mess Sherlock had made. “Now what?” he asks quietly after. Sherlock is breathing sweet air into the space between them, his skin still damp, his body perfumed with satiation. John tucks his tentacles close to his body, tries not to let them go where they want, which is around Sherlock, his waist, his thighs, his upper back.

Sherlock blinks open an eye and watches him for a long moment. “What do you mean, ‘now what?’ It’s settled, isn’t it? We’re mated now. For life,” he adds helpfully.

John blanches. “Sherlock, that’s – you’re not – you don’t have to – that’s not how it works with my kind, not really –”

Sherlock blinks open his eye again. “Well, that’s how it is with humans,” he says in his I Know More Science Facts Than You Can Even Conceive Of voice. There’s a bit of a quirk in his mouth, but there’s a different sort of twist in his eyes.

John chooses to respond to the humour for the moment, laughs and says, “No it isn’t, you git!” but he feels his own eyes show his hand, just a little, cautious and hopeful.

“We can pretend,” Sherlock says, and it’s so soft and quiet John thinks it may have snuck out on an exhale – but then Sherlock’s eyes both blink open. “We could.”

John’s breath gets tangled on the way in, caught up in his throat and his heart and his hope; it seems everything has decided to form a lump right where he needs air to flow. He swallows, swallows again. “I don’t want to pretend,” he says at last.

He sees the momentary flash of hurt in Sherlock’s eyes, before he adds:

“I’d rather choose to be mated for life. With you.”

Sherlock blinks rapidly, and his Adam’s apple bobs. “Oh.”

“Yes, you great git. ‘Oh.’” John reaches out and pulls Sherlock closer with everything he’s got, is momentarily panicked that Sherlock won’t respond – but then long arms and legs are twining with his, and shuddery breaths happen beneath John’s hands and drowsy tentacles.

“Good,” Sherlock huffs, and it’s a bit muffled, but John isn’t going to argue with the way Sherlock has pushed his face against John’s neck. “Good of you to finally see sense,” he amends. “I knew you wanted this. I saw you smiling just now,” he adds, as if that is the final proof.

John rolls his eyes and bites back a laugh. “No you didn’t, your eyes were closed!”

“I heard it, then,” Sherlock insists.

“You can’t hear a smile,” John says, but it comes out utterly fond and covered in grin and – and kisses, because Sherlock has pushed into his space until he can work his lips sloppily over John’s, exhaustion in each movement. John pulls back. “You should sleep,” he urges gently.

Sherlock tucks his head into the crook of John’s neck, bathes the skin there with a sigh. For a moment John thinks Sherlock actually listened to him, but then:

“That – has it ever felt like that. For you. Before.” Sherlock’s words buzz against John’s neck.

“No,” he says at last, resigned to Sherlock avoiding the rest he needs. “It hasn’t. I never thought I would have a Tide, to be honest. I didn’t have one back in my home water. None of this should work. My pheromones shouldn’t affect you, and you shouldn’t affect me.”

Sherlock is quiet for a long minute before he asks, “How frequently do Tides occur?”

John shrugs. “Everyone is slightly different, and besides. I hardly think we can use the average Tide cycle as any sort of guide, considering I’ve come into mine so late in life, and with a human, at that.”

Sherlock looks up at him. “Second thoughts?” he asks, and John can feel the tension just begin to creep under his pale skin.

“No,” he says firmly.

Sherlock lifts his head, seems almost incensed at John’s certainty. “No? What if you never have one again, what if this was a fluke, what if this doesn’t work –”

“And?” John asks. “I got along pretty damn well without my tentacles before, you know.”

“So –” Sherlock cuts himself off and drops his gaze. His teeth worry his lower lip.

“So?” John prompts, but Sherlock doesn’t say anything, just keeps not meeting John’s eyes – and when John catches on, he tightens his arms around Sherlock and says, “Oh, you idiot.”

“What?” Sherlock demands petulantly.

“Of course I’ll still want you. I wanted you before my Tide showed up, I was just too stupid to act on it. Too worried you’d catch on and run off.”

“Oh – so then…?” There’s no mistaking the bashful, defiant, hopeful look on Sherlock’s face.

John laughs and tips him up for a kiss. “Yes, you git, I am far from finished with you.”

Sherlock flushes and can’t quite seem to wipe the smile from his mouth.

“For instance,” John leans forward to murmur in his ear, “I don’t yet know what it feels like to have you inside of me.” This close it’s easy to hear Sherlock’s small gasp, and the damp air behind his jaw blooms with a faint shade of arousal. John slips a palm beneath the covers to feel where Sherlock’s cock is making a valiant, if unsuccessful, effort to harden.

“John,” Sherlock sighs, and it’s half complaint, half frustration.

John stops his teasing touch, slips his palm up Sherlock’s stomach and chest. “It’s ok. No rush. There’s always tomorrow,” John murmurs, lifts his hands to hold Sherlock’s face and stroke his cheekbones.

“Hmmm,” Sherlock leans into the light touches, cat-like, and John thinks he might finally have dozed off, when he blurts: “Can I name you?”

“…I already have a name,” John says. “It’s John.” John quite likes his name, thank you very much.

Sherlock’s eyes roll behind his closed lids. “I mean your species.”

John snorts. “Your people already tried to name mine – you call us ‘merfolk’ and think we all have fish tails. Seriously? Why fish tails? What good is a fish tail?” He leers down at Sherlock as he looks up. “What fun is a fish tail?” John asks, letting his right ventral tentacle curl and coil against Sherlock’s back.

The corners of Sherlock’s mouth turn up. “Mmmm. Agreed. I was, however, planning on being slightly more scientific than calling a people that live in the sea a variant of the phrase ‘sea people.’ I rather think Cephalo sapiens will suit, don’t you? And if you want, you can abbreviate it to C. sapiens, which can be read as –”

“…Sea people?” John catches half a breath, and then tumbles into laughter. “Oh god, it’s perfect – and also atrocious –” John dissolves into giggling, and Sherlock is laughing in his arms, bare shoulders shaking against his.

“Far superior to your ‘current events’ attempt,” Sherlock digs at him, and John’s laughter turns breathless.

“Go to sleep, you,” John says at last. “You’ll want to be rested come morning,” he promises, and Sherlock raises an eyebrow at him.


“Well, when I said there’s always tomorrow, I meant I’m rather looking forward to tomorrow…” John raises his own eyebrow right back at Sherlock, who laughs, a bit breathless, but finally settles against him.

“If you insist,” Sherlock says with a huff – as if it isn’t obvious he is exhausted and needs rest and is moments away from succumbing despite stubbornly fighting sleep’s pull, the way he always does – and to prove it, the huff ends as a sort of sigh as he falls quiet. It isn’t too long after that John feels the body in his arms – Sherlock – his mate – grow still and soft with sleep.

And for the first time in a long time, John thinks back to all his elders warned him of, the horrors they painted of the world, their warnings and their glowers. He thinks of the things he’s seen that match that depiction – the war, his injury, parts of his recovery. Loneliness, uselessness, and a certain sort of homelessness that has nothing to do with shelter.

Never had they mentioned he might find the other sides of those darknesses – adventure, companionship, purpose – and now this: his friend, his mate, his Sherlock, and by the smell and feel and taste of him, his home.

John settles in, and belongs.