20000 meters underwater, and I still don't have a love for it. I might like it a little if it weren't so boring, but so far, nothing has happened. The pilot of this submersible says that's a good thing, because otherwise we would be covered by millions of tons of water, and explode because of the pressure. I just think he's no fun. We could figure a way out of it, like in the Meg 2, they made it to the underwater base, and then to the surface. I just think that everyone here is boring, especially the captain. He's my dad. Ever since mom died, he's been taking me to all different places, and he's suddenly into new things. It's weird. Like, I just want to stay home some weekends, not go deep sea fishing, or sky-diving. Whatever, though. He seems like he's been doing better ever since the accident.

Thump! Something just hit the side of our sub. Whatever it was, it left a big dent. Everyone is panicking. I don't really care. If it jazzes things up a bit, I'll welcome it.

Thump! It hits again. What was that? I peer outside the small glass windows, trying to spot whatever it was. All I see is a shark fin. A shark couldn't make that dent, could it? I'm answered a second later, when another one rattles the ship, disabling all controls.

I take back everything I said about wanting things to get interesting.

The control panel is dark. Not dim — dark. Every screen, every blinking light, every digital readout that was humming along five minutes ago has gone completely black. The only light left is the emergency strip along the floor, a thin red glow that makes everyone look like they're in a horror movie. Which, considering our current situation — 20,000 meters underwater, no controls, something large and annoyed circling outside — feels about right.

Dad is not panicking. That's the thing about him that I hate and admire in equal measure. He moves through crises the way other people move through grocery stores — purposeful, calm, slightly irritated at the inconvenience. He's already at the manual override panel, shoulder-deep in a compartment I didn't know existed, talking in low urgent tones to Marco, our co-pilot, who is very much panicking.

"Controls are dead," Marco says. He says it four times. I think he thinks repetition will make someone fix it faster.

"I know they're dead, Marco," Dad says. "Hand me the secondary relay box. Yellow handle. Left side."

"What was that?" Marco asks instead of doing any of that.

"Yellow handle," Dad repeats. "Left side."

I press my face against the porthole.

The shark fin is gone. Whatever I saw before — and I'm now questioning whether it was a shark fin at all, because shark fins don't typically leave dents the size of a refrigerator in reinforced titanium — has moved out of the narrow cone of our exterior floodlights. Beyond that cone is pure black. Not dark like a room with the lights off. Dark like the concept of dark. Dark like the universe before anything decided to exist.

Something moves in it.

I can't see it exactly. It's more like — a displacement. A sense of mass shifting. The water outside the porthole changes, very slightly, the way water in a bathtub changes when you move your hand through it. Except this is not a bathtub, and whatever is moving through this water is not a hand.

It's big.

I don't know how I know that. I just know it the way you know, before you've even fully woken up, that something in the house is wrong. Some animal part of my brain that doesn't speak in words is simply transmitting the information on a loop: big big big big big.

"Hey, Dad."

"Not now."

"Dad, something is—"

"Not now, Ellie."

I step back from the porthole. Fine. I'll file it under Things Dad Will Wish He'd Listened To, along with the kayak was making a weird noise and I don't think that weather app is accurate.

Dr. Vasquez appears from the rear compartment. She's our marine biologist — the reason we're down here in the first place, collecting water samples and cataloguing deep-sea organisms with her team. She's in her forties, small and precise, with the kind of face that looks like it doesn't waste expressions on things that don't deserve them. Right now her face is doing something I haven't seen it do in the two weeks I've known her.

It's afraid.

She walks straight past Marco, who is now just holding the yellow-handled relay box and staring at it, and comes to stand next to me at the porthole. She looks out. For a long moment she doesn't say anything.

Then she says, very quietly: "How big was the fin?"

"I don't know. Big?"

"Bigger than the sub?"

I open my mouth. Close it. Think about the fin I saw — how it had filled the porthole, edge to edge. Our sub is eleven meters wide.

"Yeah," I say. "Maybe."

Dr. Vasquez nods slowly, like I've confirmed something she already suspected and desperately hoped was wrong. She straightens up and turns to my dad.

"Captain Reeves," she says, in a voice that is very controlled and very serious, "I need you to not turn the exterior lights back on when you restore power."

Dad looks up from the compartment. "Come again?"

"When you get the systems back online," she says, "please don't switch the exterior floods back on. Keep us dark."

"I need the floods to assess hull damage," Dad says.

"I understand. I'm asking you not to."

They look at each other. Dad has about forty different expressions for I disagree with you but I'm evaluating whether to say so, and he runs through at least six of them before responding.

"You want to tell me why?"

Dr. Vasquez glances at me, then back at him. "Certain organisms in the deep mesopelagic and hadopelagic zones are sensitive to bioluminescent and artificial light sources. Attracted to them, in some cases. Aggressively."

Silence.

"The dents," Dad says.

"Were likely investigatory," Dr. Vasquez says. "It bumped us. It may have moved on." She pauses. "The lights might bring it back."

"What," Marco says, "is it?"

Dr. Vasquez doesn't answer. She's looking out the porthole again.

That's when the sound starts.

It's low — lower than low, really, more of a vibration than a sound, something you feel in your sternum and your back teeth before you actually hear it with your ears. It rises slowly, cycling through frequencies, and for one completely insane moment it sounds almost like language. Like something enormous trying out different pitches, searching for the one that carries.

The sub shudders.

Not from an impact this time. From the sound itself.

"It's communicating," Dr. Vasquez says. She sounds terrified and fascinated in proportions I find deeply uncomfortable. "It's using low-frequency pressure waves to — it's echolocating us. Or — or calling."

"Calling what?" I ask.

She doesn't answer that either.

The vibration fades. Silence floods back in. The red emergency lighting hums. Everyone stands still, and the darkness outside the porthole is absolute and patient and enormous, and I think about that displacement I saw — that sense of mass, of something vast and slow rearranging the water around itself — and suddenly I understand exactly why my dad became the kind of person who takes his kid deep sea diving and skydiving and to every corner of the world he could think of.

It's not about the places.

It's about not sitting still long enough for the grief to catch up.

I look at him across the cramped, red-lit cabin, and he's looking at me, and for just a second, neither of us is thinking about the thing outside.

Then something massive and dark slides past the porthole — a surface, close enough to touch the glass, textured like nothing I have a word for — and every thought evaporates.

It's not a shark.

It's not anything that has a name yet.

It moves past slowly, almost leisurely, and in the second before it passes out of the thin ambient light and disappears back into the black, I see one thing clearly:

An eye.

The size of a dining table. Ancient. Depthless.

Looking directly at me.

And then it's gone, and the water is still, and somewhere in the dark below us — far below, in depths that don't have names, only numbers — something calls back.

Dad gets the power restored forty seconds later. He does not turn on the exterior floods.

Nobody suggests that he should.