For as long as Noor could remember, the ocean had been her lullaby.

Her Papa, a fisherman in a long line of fishermen, had the uncanny ability to read the rhythm of the boat’s rocking. Blues today, he would say without preamble from the other side of their tiny kitchen table. Or soul, or rock, or once he was even specific enough to say, Mozart. Do you hear Mozart, Noor?

And then there were nights, once the storm had broken, when their little sailboat house rocked back and forth in time with the crashing waves, when Papa would wrap a blanket tighter around her shoulders, pull her into his arms, and whisper, Do you hear them, Noor? Do you hear the selkies singing?

Selkies – women with the power to shapeshift into seals. Noor’s belief in them only wavered when kids at school laughed behind their hands about the silly superstitions of Cassandra’s fishing families – boat rats, people called them, the affection in the phrase varying depending on who said it. Even if she’d never seen a selkie, it wasn’t difficult to believe on stormy nights, when she could hear their throaty song crest and fall with the sea’s choppy waters, just audible over the rain pounding the deck above. In the morning, Noor would take out her little piccolo and try to recreate the music, but no matter how much she ached to, she could never quite mimic it.

Papa often went inland to the city for business – Noor had been staying behind since she was old enough to. Being onshore felt like being away from a piece of herself. And this particular time should have been no different, except for the storm. Not expecting it, Noor had taken the boat out to sea, where Cassandra’s lighthouse was only a dot in the distance. She had lived through plenty of ocean storms. The rise and fall of a boat had always been Noor’s cradle; she was a fisherman – well, fisherwoman – and she refused to be afraid, but she couldn’t help but bury herself deeper in the blankets as the porthole rattled in its frame and the sail clips clanged against the mast overhead.

The room lit bright with lightning, and the thunderclap that followed seemed to echo. The boat rocked; Noor’s hot chocolate sloshed in its canister, and she heard several things in the cupboard come loose from their Velcro bindings and roll around.

Suddenly the hatch ripped open.

Freezing rain and seawater surged in before the wind slammed the door closed again. Noor threw back her blankets and rushed secure it, but not before she heard something shrill among the thunder and waves.

A scream.

Noor’s stomach turned. She hesitated, watched her Papa’s yellow Sou’wester rainhat jump from its hook in the next roll of the waves. Then she shoved her feet into her rainboots, slung the life preserver over her shoulder, and barreled out into the storm.

The sudden force of the wind nearly tossed Noor off her feet, and she snatched at anything she could reach to keep her balance. It was dark as pitch, and the battering rain made it impossible to see. The only exception was the brief flashes of lightning, and the tiny wink of the lighthouse in the distance.

“Hello?” she shouted, but the word was ripped to nothing as soon as it left her throat.

Noor inched her way portside. The deck was slick as ice, and in one heart wrenching moment she lost her footing and slid toward the yawning darkness below before her body slammed into the railing and she righted herself. The water churned, frothy waves like flashes of sharks’ fins.

Finally, at the stern, Noor heard the cry again. A head crested the surface, mouth agape, before tumbling back under.

“Here! Grab on!” Noor shouted, and threw the life preserver as far as she could. A pair of pale hands scrabbled to hold on, and Noor shouldered the rope and painstakingly pulled the preserver back, until the girl on the other end could grab the ladder. Noor threw the rope aside and dove for the girl. She was little enough that Noor could heave her onto the deck and carry her into the cabin.

The hatch closed. The storm’s screaming muffled.

Noor lay the girl on the couch. She was naked, her skin pearly white and starkly pale against a tangle of black hair that seemed to shift and glimmer like an oil spill. It wasn’t black, Noor decided, it was green. Or purple? Or blue? The girl couldn’t have been older than eleven or twelve, only a few years younger than Noor.

She gasped, choking, while Noor wrapped her in towels and blankets.

“Are you okay?” Noor finally asked. She held out a knit sweater. For a moment the girl just stared, expression plaintive, before she pulled it over her head. “What’s your name?” Noor asked, when the girl didn’t respond.

“Isla,” she said, and then burst into tears. She blabbered in a foreign tongue between sobs. The air made it sound strange, like maybe the words would make more sense if spoken underwater.

Noor went to hug her, pulled back, then finally settled for an arm pat. “It’s okay. You’re safe here,” she said. “I’m…I’m Noor.”

Isla sniffed. “That’s a pretty name,” she said in a heavy accent Noor couldn’t place. A dribble of snot trailed from one nostril, and Noor gently wiped it away, the way her Papa did when Noor was sick in bed.

“Are you…” Noor took a deep breath. “Are you a selkie?”

Isla’s head shot up. “How did you – ?”

“My Papa and I listen to you guys sing at night. It’s…it’s beautiful. I –” Noor’s gaze swung away, suddenly ashamed. “I’m trying to learn the songs.”

Isla’s mouth quirked, and Noor’s stomach soured. Was she making fun of her? But then Isla looked back down at herself, a lock of wet hair clinging to her temple like a strand of seaweed, and she dissolved into tears again. Waves crashed beneath her long sobs in a way that reminded Noor of the soulful, clarion songs she heard over the ocean.

“I – I got separated from the others,” she cried. “And now…now I can’t change.”

“Can’t change? You – you can’t change into a seal, you mean?”

Isla nodded. Her cheeks – smattered with freckles not unlike those on a seal’s hide – were flushed. “I’m not good at it. I’ve only ever been human for a few minutes at a time and I – I can’t…”

In that moment, even though Isla looked human, had a body with five fingers and toes, and hair that went frizzy as it dried, Noor sensed fathoms between them. As much as Noor called the sea her home, for Isla it really was. The realization felt like vertigo. Instead of speaking, Noor opened a sleeve of crackers and showed Isla, who’d never had human food before, how to spread cream cheese on top. Eventually the storm faded, and the creak of the boat lulled them to sleep.

In the morning, Noor started a hot shower for Isla and radioed the station with a message for her father.

“I brought you a towel,” Noor said after, pushing the bathroom door ajar. “It was over the heater, so it’s nice and – hey, what’s wrong?”

Isla was crouched on the shower floor, crying softly. A mixture of blood and water ran down her legs and swirled around her feet. A slimy clot clung to the drain, and the sight of it made Isla sob harder, her complexion pale.

Noor dropped the towel and rushed forward, turning off the water. “Are you hurt? What happened?”

Isla buried her face in her hands and shook her head. “I don’t know, I don’t know! I – I just started bleeding – ”

“From where?”

“I don’t know, I don’t – ”

“Is it…is it your period?”

Isla finally met her gaze, eyes wide and doleful with tears, dark as the far side of the moon.

Noor knelt in front of her. “Do you know what that is?”

Isla shook her head.

“Oh. You really haven’t been a human much, have you?”

Isla’s lip quivered, and Noor hurriedly pat her shoulders. “It’s fine!” she said. “It’s fine. I only had my first one last year, and I didn’t know what it was either. Most human women get them.”

Isla wiped her nose on her shoulder. “But I’m not a human. At least not very often.”

“Well…you are right now, aren’t you?”

Isla just stared at her for a long moment, and Noor worried she would start crying again, but instead she just stood and picked up the towel.

Noor helped Isla clean up. They made tea, which Noor always drank during her periods, and sat above deck, cupping warm mugs.

“Do you have parents?” Noor asked. “Who can teach you things?”

Isla studied the steam coming off her tea. The vapors, like tiny ghosts, swirled away into the cool ocean air. “Yeah. But human things never seemed to matter much.” She sighed. “I need to go home.”

“The wind is taking us to shore. Maybe you can turn back then,” Noor said.

“Yeah,” Isla said. Her long hair caught in the breeze. She was awkward tucking it away, like it wasn’t a gesture she was familiar with. “Did you say you were trying to learn our songs?”

Noor felt her cheeks burn. “Oh. Yeah. I know it’s dumb.”

“It’s not dumb,” Isla said. She grinned suddenly. It was the first time Noor had seen her smile, really smile. “Can I hear?”

“…It won’t be as good as yours.”

Isla clasped her hands. “Please?”

“Well…okay,” Noor relented.

She retrieved her piccolo and sheet music from the cabin. She could feel Isla watching as she set the instrument to her lips and gave a tentative blow. The note screeched, and they both winced. Noor gave an apologetic smile and tried again.

The song came easier the second time. It was one she heard most often when the sea blushed post-storm green. Noor had been born on the water just as her father had – and his father and his and his – and to her the selkie song sounded like home. The only reason she looked at the sheet music at all was so Isla wouldn’t think she’d cared enough to memorize it. Which was almost true – Noor hadn’t tried to memorize it – but doing anything enough times inevitably imprints it on your heart.

But here on the open water, with Isla gripping the boat railing, Noor didn’t feel like she held any claim to the song anymore. How could this song – and the ocean that came with it – be her home, when a real selkie stood next to her, eyes wet with homesick tears? As much as she thought she did, Noor never knew the ocean. Not like Isla did. And she never could.

And no matter how much Noor practiced the song, her little woodwind could only get so close to the real thing.

Right as Noor was about to quit, a voice chimed in.

Noor started, but didn’t dare stop playing. Isla faced the water, eyes closed, singing in that language Noor couldn’t understand, but was somehow as familiar to her as the veined pattern on the inside of her wrist.

Up close, the selkie song seemed to make the air tremble. Noor’s arms prickled with goosebumps. She’d had never had the courage to play in sync with the voices that carried over the sea – but now it felt like the only way to play.

The song ended in a trailing note that lingered in the air long after Noor’s lips left her instrument. They were both quiet until Isla threw her arm around Noor’s waist without preamble.

“That was beautiful,” she cried. “See? You’re really good!”

“Thanks,” Noor said, feeling a little dazed. “Still not as good as yours, though.”

Isla drew back and leaned against the railing. She held her hand over her mug, and they both watched the steam swirl around her fingers. “You’re good at both,” she said.

“Both what?”

“Human things and selkie things.”

“Well, you can’t really mess up being human,” Noor said. “You just do it.”

Isla looked out at the water, her only response a thoughtful hum.

The boat reached shore by noon, and in the evening they stood on the dock’s edge, the night-dark sea beneath them. It stretched out into infinity, a piece of the sky caught on Earth, the moon’s reflection rippling like spilled milk across its surface. Every so often, the distant lighthouse sighed yellow.

“Look at this,” Noor said, and led the way onto the rocky shore. Solid ground felt uncertain under her feet after so many hours on the boat. She helped Isla over a boulder then pointed into the distance.

The tiny town of Cassandra glimmered back at them, nestled between hills. There was a tiny church steeple, a lone car passing through an intersection, the headlights mere pinpricks of light. Warmly lit windows dotted the horizon. The mainland seemed to emit a careful glow, an ember burning softly in a hearth.

“It’s beautiful,” Isla said.

“It is.”

Isla looked down at her hands knotted in front of her. “I think it’s time for me to go.”

“You think you can turn back now?”

“Yeah,” Isla said, and smiled up at her. “I think I can.”

“What changed?”

“I love crackers now.”

Before Noor could reply that crackers probably weren’t much related to mythical shapeshifting, Isla pulled her into a hug so tight Noor lost her breath. “I’ll see you again soon,” she said. “And I’ll be listening.”

“Listening?”

Isla grinned. “For your song!”

Noor smiled despite herself. “I’ll be listening for yours too.”

With that, Isla climbed down the boulder and picked her way over the pebbly beach toward the surf. She looked back only once, to wave, before she dove into the sea. Somewhere between one crashing wave and another, Isla the girl was no longer a girl, only a dark shape slipping through the water.

Then she was gone, and Noor was left atop the boulder, the sky above her, the sea and land below.