Today was a wonderful day. The breeze was warm, the waves were calm, the sand — Armin wriggled his bare toes experimentally — the sand was especially sandy. He wasn't usually allowed to walk the shoreline without his parents or grandfather, but this summer, he had been granted the privilege. It made Armin feel quite grown-up. Grown-up enough, even, to steel his courage and wade out to the interesting-looking rock that was just off-shore; that was just big enough for a very grown-up seven-year-old with a backpack heavy with books and a sandwich bag full of goldfish crackers to throw to the fish.
He marveled at the view — it wasn't terribly high, certainly, but it was farther out into the waters than he'd ever been. The ocean floor dropped off into green-blue depths, and iridescent little fish glinted beneath the surface, shimmering in the afternoon sun. His heart fluttered at the sight.
He unzipped his backpack and retrieved his reference book, and lay on his stomach, settling in for a long afternoon. He tossed a handful of goldfish crackers into the waters, and eagerly flipped through the pages. Slender body with a small, pointed head, last dorsal ray not elongated, Elops saurus. Found inshore in bays and estuaries, frequently schooling in tidal pools, often confused with juvenile Megalops atlanticus. Diet consists mainly of fish and crustaceans.
And crackers. Armin stifled a giggle as he watched the fish swarm around the school of crackers, nibbling hesitantly before devouring them in one bite. He threw a fresh handful of crackers into the water, and rested his chin on his hands to watch the feast.
There used to be so, so many fish, and corals, and dolphins in the deep waters — his grandfather had told him stories in the summers before, as they walked the shoreline hand-in-hand. But, people fished too much, and built too much, and rode their boats too much. It hurt the ocean, and the fish and corals and dolphins couldn't live there anymore. Armin had gazed off into the quiet waters, and swore, swore with the determination that only a child could muster — he'd study hard, and go to school, and he'd be a marine biologist that would study the ocean; fix it back up so the fish and corals and dolphins could come home.
Armin squinted into the waters, shaken out of his reverie. The fish were wriggling away from the remaining crackers, and the remaining crackers were…
Unnaturally green eyes stared at him from beneath the waves. It was…a little boy, about his age, and he looked like he didn't have any clothes on. He also looked like he didn't have any legs. He had a tail, a long, shimmering green tail, green as his eyes and with long, pointed fins. The boy slowly rose to the surface, poking just his head above the water, up to his nose.
Armin and the boy locked eyes, staring for an agonizingly long moment. The boy's gaze flicked to the bag of crackers in Armin's hand. Armin slowly took another handful, and held them out.
"Here," Armin whispered, voice quavering only a little. "H…hold out your hand."
The boy drew his hand from the water, and held it out. His arms were covered in those shimmering green scales, too, and his fingers, oh, they were webbed like a frog's, but his five fingers looked human, and his hands looked human, and his face looked human…Armin delicately surrendered the handful of crackers to the boy, and laughed helplessly, joyfully as the boy plopped back underwater to enjoy the snack. Once he finished, he swam in a long, lazy circle before returning to the surface, resting his hands against Armin's rock. The way he moved was nothing like anything Armin had seen before, not in the movements of fish in the little tidal pools, not in the movements of dolphins on TV — he moved almost like an eel, but, well. Armin had never seen an eel that looked this pretty.
"My name's Armin," Armin said, quietly. "Do you live around here?"
The boy stared, unblinking. Armin supposed many fish couldn't blink.
"…I'm Eren," the boy said. The blink that followed was long and almost exaggerated. Ah, so he did blink. That was good; Armin would have been a little creeped out otherwise. "I live out farther. There isn't enough food to live here."
"Oh." Armin thought for a moment, then offered his sandwich bag. "Do you want more crackers?"