Rucker Little, now essentially in charge along with Chester Fishwick, nodded from the bank. “We’re coming. We won’t let you scuttle her by accident, we can promise you that. You do your job; we’ll do ours.”

Cly gave them a nod and a small parting salute as he flipped his leg over the hatch’s round entrance and disappeared down inside it.

He drew the lid shut behind him, settling it as tightly as he could against the seal, then drawing the wheel hard to the right to compress that seal, and lock them all dry inside. As he did so, he felt a strange vacuum settle and he recognized it — he knew it from years of gas masks sucking themselves into position against his face, and from the layers of filters and seals that preserved Seattle’s underground. He knew the feel of it, but here, somehow, it felt more sinister.

In the underground, up above there was only a street — only a city filled with poison air. But that poison air could be cleaned. No one would drown in the street. All it took was a mask to make the city navigable, never mind the rotters and the blinding clots of fog.

But not here.

Not in the water, where once the ship had been lowered, there was nothing above, nothing outside, nothing touching it but the suffocating weight of liquid.

In the previous days, it’d only been practice — only puttering around the lake and learning the controls. This was different. This was the Great Muddy, Old Man River. This was bigger, or at least longer. And maybe deeper, for all Cly knew. Definitely stronger, moving with its unrelenting current from somewhere up North to somewhere beyond the delta, meeting the ocean west of Florida.

He ducked down into the main body of the interior, where red, orange, and small gold lights flickered, brightening the interior, but not much. The dimness was necessary, for two reasons.

First, no one wanted any other craft to take notice of an odd glowing presence beneath the murky waves. And second, if the interior was too bright, the windows would be useless. It was very dark beyond the six-inch-thick glass, but with a small row of encouraging sunset-colored lights mounted externally beneath the watershield — beaming like a tentative smile — it was possible to spy the largest obstacles without being spotted from above.

They hoped.

They’d tested it out after dark on Pontchartrain, but the results had been inconclusive. The ship’s visibility depended on too many things — how many other craft were present, what other lights were bouncing, reflecting, shimmering on the surface. They all quietly prayed, or wished, or crossed their fingers inside their pockets … taking it on fervent faith that the small fleet of pontoons, airboats, and skiffs above could hide them.

“How’s it looking?” Cly asked, taking a sweeping assessment of the room.

Fang signed with one hand: All ready.

Deaderick Early was standing by the window, looking out into the swirling mud and dark, dirty water. Without turning around, he said, “We’re as ready as we’ll ever be.”

Cly said, “Then everyone needs to buckle down, if you can. We’re pushing out into the water, and we don’t know how hard the current’s going to take us. Early? I might recommend that you take a seat there at the window, so you can still serve as underwater lookout. We’re running low on chairs at the moment, but you’ve got handholds there.”

Wallace Mumler sighed. “Just one more thing we’d like to improve in future models. We don’t need for it to be a luxury steamship in here, or anything like that. But it’d be nice to have extra sitting room for the occasional passenger.”

Deaderick said, “Agreed, but for now, we’ll work with what we’ve got. Wally, make yourself at home by the low right port, will you?”

“Already on it, sir.”

A series of taps on Ganymede’s dome sent the message that the folks up top were ready to serve as guides, this crew of Charon’s helpmates, paddling, pulling, tapping, and running small diesel motors that sounded awfully loud, but weren’t, in the grand scheme of the river’s mumblings. Up above, Cly could hear them starting, one by one. The low putter of the motors and the screw propellers from the two or three antique steam engines designed in miniature … these noises filtered inside, and in the submarine’s belly it all echoed, muted and muffled.

“Turn down the lights as far as you can — but not so far that they won’t do us any good,” the captain ordered. Houjin went to one concave wall and threw one set of switches; Wallace Mumler reached up and grabbed the other set. With the flickering fizz of electrics dimming, the interior dropped to a low, golden glow.

The men in their chairs were shapes and shadows, man-sized cutouts of utter black in the charcoal gray of this scene, offset against the wide, bulbous windows that gazed out into the darkness of the river’s underside. But from under the window, the smiling lights glowed, struggling hard against the silt to provide some guide, some illumination.

Morse code taps bounced down from above.

“They can see the lights,” Deaderick said.

“Yeah, I heard it,” Cly acknowledged. “But we’re not all the way under yet. We’ll shove off and get some depth, and maybe they won’t be quite so clear. That’s what I’m hoping, anyway.”

More taps. A quickly sent word of readiness.

Cly took his own seat and strapped himself down. “Engines up, Fang — don’t burn the bottom propeller; we’re still right up against the shore and I don’t want to screw us into the bank. Use the side thrusters above the charge bays. All we need is a nudge.”

Fang nodded, and his fingers flew across the levers with their knobs and buttons so faintly alight that they could barely be described as such. A hum rose up, accompanied by a curtain of bubbles that brushed by the edges of the huge forward windows.

“They aren’t synched,” Cly reminded him. The side thrusters were made to steer, not propel. There was no mechanism to make them fire in time with one another.

Fang didn’t nod this time. He didn’t need to. He needed only to lean his wrists forward, perfectly in tandem, and with a tiny lurch, Ganymede pulled itself away from the bank, away from the sunken winch, and away from the improvised dock at New Sarpy.

Slowly at first, the ship crawled forward. Then, as soon as the riverbed had dropped away before them, Cly positioned his feet on the depth pump pedals and began the nerve-racking work of letting the craft drop, inch by inch, deeper into the river. At the top of the wide forward windows, a small seam of water sloshed outside, at the level where the craft’s crown hit surface. This jiggling seam of inky water crept higher and higher, until it was gone.

And at last Ganymede dropped below the waves with one gigantic slurp.

They were in the river. There was no air except what they had in the compartment, and what would be pumped down every so often to cycle what they breathed.

It made Cly’s skin crawl, and Kirby Troost’s, too — the captain could see it when he glanced over at the engineer. Troost looked queasy. One arm over his stomach. One hand over the weakly illuminated dial that showed how far down they’d come, and how much farther they could reasonably go.

Houjin, on the other hand, was vibrating with excitement. They’d stationed him at the mirrorscope he’d liked so much upon first encounter; now it was his job to stay there and report what was coming and going whenever it was safe to leave the tube up in the open air. He turned it side to side, a voyeur to adventure, and the metal tube’s joints squeaked despite their fresh greasing.

“What do you see?” Troost asked the boy.

“The other boats — the little ones, the rafts and skimmers. They’re moving into place and coming up behind us. Ooh! Norman sees me looking at him! He’s waving us forward.… He wants us to pull ahead.”