The man with the white streak in his black hair was diving too close to her again. He was a powerful swimmer, for a human. He kept pulling down through the water with strong arms and hands, propelling himself with big kicks.

The sea creature tried to quiet her trembling limbs, so that if the human got deep enough to see her, he would think she was just a mountain of moss on the ocean floor and would turn away and stop scaring her.

Then the human shot back up to the surface. The creature relaxed, relieved that humans needed air. Especially this human, who was different from the others. Most humans jumped out of a boat, thrashed around in the water looking like birds trying not to fall out of the sky, then dragged themselves back into their boats, satisfied. The sea creature never saw them again.

But this human returned frequently, and dove with a purpose that frightened the creature, for she kept treasures here on the ocean floor, gathered them, guarded them, and this human knew about one of them. He didn’t know about her. No one knew about her. But he wanted the object that was her favorite treasure. She could feel him thinking about it. She wound her long tentacles around it, trying to hide it from sight. It was a ship.

This ship, two-masted with swirling sails, had dropped nose-first from the waters above not too long ago, and landed beside her. All the creature’s treasures—nets, harpoons, anchors—sank like this, from the bright water above. But ships were rare treasures, and this ship was extra-special, for when she pressed one of her eyes to a porthole, she could see a secret world inside. A pink room with tiny sofas and armchairs attached to the floor, paintings on the walls, lamps; a skylight crossed with bars and a door with a sparkling knob and hinges; and two pink-skinned human bodies, which were beginning to look soft and puffy. She called it her Storyworld.

The most special and unusual thing about her Storyworld was that there was a padlock on the outside of the door, trapping these bodies inside. Usually, when a ship sank, the people jumped into the water or the lifeboats, trying to live. They didn’t close themselves into a room with a padlock.

The human with the white streak in his black hair, who had brown skin, dove deep again, looking for the ship. He thought about a woman sometimes as he dove, a human woman with dark braids and gray eyes who wore glimmering rings on pale brown fingers. The sea creature understood that he wanted the ship so he could give it to the woman. The sea creature didn’t like this woman, not at all.

The diver’s own boat was a small oval above. She thought about grabbing its anchor and pulling. It was not the sort of thing she ever did. If she pulled his boat under, he would probably see her, and she never attracted anyone’s attention. But then, eventually, he would drown, and that would make him stop looking for her favorite treasure. In fact, he himself would make a fine treasure. In addition to the nice way his hair floated around his face, and in addition to his tiny, perfect muscles, his tiny, perfect hands and feet, a red jewel sparkled on a ring on his thumb. The creature would like to slide that ring from his thumb and wear it at the tip of one of her thirteen tentacles. She loved the sparkly things humans wore. And then the man would bloat, and rupture, and rot, and eventually become a smooth, shiny skeleton in tattered clothing, and she loved that about humans too. She could add him to her collection of bones. Encircle him with her tentacles, keep him safe.

Then a pod of silbercows approached, so she decided to leave the human’s small oval boat alone. Silbercows never let humans drown, if they could help it. Silbercows were about the size of one of the sea creature’s eyes. They made platforms with their backs and lifted drowning humans to the surface, thinking encouraging thoughts at the humans. Also, now the chance of being seen was too great. Silbercows had better underwater vision than humans.

Again, the human broke his dive and ascended to the surface. Next, the human seemed to be playing with the silbercows, swimming and rolling with them, laughing, shouting in happiness. This happened pretty often with this human. The silbercows liked to visit him, and he always laughed a lot.

Then, without warning, something extraordinary happened. Two new humans crashed into the water from above, attached to long ropes. They grabbed the laughing human, struggled with him. He fought, punched, kicked, twisted. He was marvelous; she waited for him to break away. But then he seemed to run out of air, for his body went still. The other two humans shot out of the water on their ropes, lifting his body with them.

The creature was so flabbergasted that she rose some distance from the ocean floor, balancing on her thirteen tentacles and reaching around with her twenty-three eye-stems. Through the wavy glass of the water above her, she could make out the form of an airship heading north across the sky.

Then, remembering the silbercows and not wanting to be discovered, she sank back into the darkness at the ocean floor. They didn’t notice her; their purple-blue faces were stretched above the surface, their big, dark eyes watching the limp man being carried by the airship. Their mental voices were raised in a song of distress. They communicated in pictures and feelings, not words, but the creature understood their meaning. We see you, friend, they were crying. We know. We will tell.

The creature, when she scavenged for treasure, went to dark places, because she didn’t want the silbercows to see her. The silbercows were surface animals, creatures of the light; she was a creature of the depths, a sneaker, a crawler, a dragger. There were animals who saw her in the places where the creature liked to go, pulling herself forward with her long tentacles, but they weren’t the kinds of animals whose attention mattered.

Today she crossed the field of pink and white flowers and slunk into the forest of filaments and reeds, where the seahorses peered out of their swaying caves. Seahorses forgot about things once they could no longer see them. Sometimes, when they saw her, they unwound their tails, shot back into darkness, then forgot and came forward again.

The creature was thinking about the human with the white-streaked hair, the humans who’d grabbed him, and the silbercows who’d called out to him. We see. We know. We will tell.

See what? Know what? Tell whom? The creature didn’t want the answers to these questions. She was relieved to live in the deep, away from the light where animals interacted and interfered with each other.

She reached the place where clumps of moss gathered against the base of coral mountains. The sponges who lived here had tiny, bright, sharp minds full of silly words. Keeper! Friend! Hero! Keeper! Music! Laughter! Dance! Keeper! Keeper!

They sang in a chorus around her every day as she brought moss to her mouth with her tentacles. She was so used to their song that she paid it no attention. Sponges weren’t very smart. Once, when she’d tried to eat one on a sudden, curious whim, it had screamed with laughter as she’d tried to pull it from its pillar, as if she was tickling it. Keeper! it had cried. Games! Jokes! Fun! She’d given up, let it go, and returned to ignoring them.

Usually, after she ate, she scavenged for treasure in the murky pits beyond the coral mountains. Today, though, the creature didn’t need to scavenge, for the same currents that brought her food had brought a treasure. It was a little thing, a ball of metal, bobbing and tapping against the coral. Human-made, but not an object the creature recognized. Egg-shaped, with a tiny circle of metal at one end that was attached to some sort of pin. The circle and the pin were shiny, which was pleasing, though nowhere near as pleasing as the sparkly red jewel on the thumb of that diving human.

The creature picked the thing up and held it to her eyes. She caressed the metal circle, wondering if something happened when you pulled it, for sometimes human-made objects did things, if you touched them in the right place. One of her treasures was a box that opened and closed. Another had a chain wound around a cylinder, and a handle that made the whole thing turn; at the end of the chain was an anchor that thumped and dragged along the ocean floor when she played with it.

She would save pulling the metal circle as a treat for later. She carried the thing home and added it to her treasures.

It was nighttime when the creature woke to an unfamiliar perception. On the moonlit surface far above, the silbercows were crying out in their sleep.

Confused, she stretched her neck and swiveled her eyes. Overhead, lights flashed, thuds sounded, and suddenly, screams of silbercows stabbed at her mind. The screams galvanized her body, sharp and electrifying, the silbercows crying out in heartbreak, desperation, as had never happened before. The creature was so overwhelmed by the pain of the silbercows that she did something she’d never done. Rising to the surface, she lifted her eyes above the water.

Below a blanket of stars, humans in small boats were thrusting spears into silbercows.

The creature ducked below the surface again. What was this? No one ever killed silbercows!Hide, she thought to herself. Hide! Make it go away.

But as she tried to sink back down to her treasures, four silbercows, escaping, zoomed past her. They saw her, suspended in moonlit waters. They stared at her in amazement.

Pretend I’m not here, she begged them, trembling in every limb. Pretend you can’t see me.

Are you the Keeper? they cried, throwing their pain at her, washing against her with their...