Then we are inside the dormant central vent of the volcano. Sheer stone walls soar upward, forming a cone-shaped cathedral of glistening black rock. I feel like I’m standing inside a gigantic hollowed-out chocolate drop. There is no floor—just a pier jutting into a wide circular lake.

Above us, dozens of dragonfly drones buzz through the air, their metal wings flickering in the glow of their jeweled eyes. Are they there for surveillance, or to provide light? Maybe this is just where the robo-bugs hang out when they aren’t piloting boats into the atoll or escorting lost freshmen through the base.

The lake is illuminated, too, from below. Clouds of what look like phytoplankton shimmer in the depths. I’ve seen bioluminescent blooms before, but they are usually blue. These tiny creatures, whatever they are, form thousands of constellations of orange, green, red, and yellow, as if the lake’s entire biome has decided to hold a Holi festival. I wonder if my parents saw this, and if they had the same thought. Did they die surrounded by these bewildering nebulae?

Next to me, Ester makes small whimpering noises. Top goes on high alert, sitting in front of Ester and giving her a quick yip that says, Hey, it’s fine. Cute dog right here. Nelinha whistles under her breath. “Vixe Maria.”

I force my eyes to follow her gaze along the length of the pier to the vessel moored at the far end.

The Nautilus is like nothing I’ve ever seen. It’s difficult for me to even think of it as a submarine.

Granted, I’ve never been on an actual sub. That training doesn’t start at HP until the second half of our sophomore year. But I have seen and studied submarines. Most modern ones look like sleek black tubes with barely any surface profile—just the gentle curve of their topside and a single con tower or “sail.” The largest ones in the US Navy can be over six hundred feet from nose to rudder, about the length of two football fields.

The Nautilus is about half that size, though that still makes it a big ship. It appears to be tube-shaped—I remember Jules Verne described it as a giant cigar—but it is neither black nor low-profile. Its hull is made from interlocking panels of nemonium, glistening like abalone shell. Intricate coils run along its sides, interspersed with bristly clusters of filaments and rows of indentations that remind me of the vibrissal crypts on Socrates’s skin—electroreceptors that allow him to sense his environment.

I can’t imagine how a hull so complicated and delicate-looking could have survived intact since the 1800s. It looks like the skin of a sea creature—something between a lionfish and a dolphin.