"Okay," said Tris. "So you're on your own. You should be used to it."

Shattering the fish tank by blasting off one corner using Doc Joyce's handgun, Tris watched as one after another of the catfish flooded out of the glass wall and into the water now lapping around her knees. And one after another the catfish stopped swimming, became rigid, convulsed and died.

She'd got it wrong again. She should have tried a side wall first. Something stocked with smaller fish. Frantically Tris tried to scoop up the last of the big beasts but there was nowhere to put it and the fish slipped out of her hands before she had time to work out what to do next, going rigid even as she was reaching for it.

Salt water had mixed with the fresh and cold with the warm. There were no catfish left to help. So when Tris realized that the exit had jammed less than halfway open and the gap was too narrow to let her fight through the incoming water, she almost didn't bother to save herself.

All the same, bulkhead lights still shone with an amber glow that endless members of a Chinese crew had once come to associate with being ripped open and left to drift towards the tectonic plates of a distant darkness. And that glow also meant the yacht's emergency systems might still be operable.

Rejecting the idea of trying to squeeze through anyway, Tris did something far more sensible; she jammed the blue marble back into position inside the table, flinching in anticipation of an electric shock that didn't happen.

"...‘get out’," finished the yacht, then it swore. "No," it said, "forget it. We can deal with you being an idiot later." The sliding door, which had begun to open, hesitated and then hissed back on itself, locking tight. Lights came up and the table Tris had left open ran a series of rapid lights, ending in the squawk of a klaxon that shut off as soon as it began.

"Okay," said the yacht. "This is the way it's going to work. I'm going to open that entrance/exit completely this time. And you're going to do nothing until I tell you. What are we going to do?"

Beyond the hull a rock ground itself along the side of the yacht and as the cabin lurched water slopped across the floor in a low wave.

"You're going to open the door," Tris said through gritted teeth, "and I'm going to do nothing."

"Good," said the yacht. "Now once the door is open, you reach inside the table and take the memory. Only this time I'll shut down first. Understand? You don't touch anything until the pretty lights disappear. Otherwise you'll get hurt."

"I'm not a child," said Tris crossly.

The yacht considered this for all of half a second. "Yes, you are." Its voice was matter-of-fact. "At least, you are according to any definition I've got on file. Now you wait," it stressed, "until the entrance/exit is completely open, then you get out fast and let yourself drift downriver, don't try to swim for the bank."

"Why not?" Tris asked, but the door was opening and the lights had dimmed. An inrush of water was her only answer. Grabbing the memory, Tris began wading towards the door only to discover that every forward step she took swept her three steps back again. "Think," she told herself.

Tristesse al-Heliconid was in her mid to late teens, small for her age and less grown-up than she imagined. She wore her hair cropped short and her breasts small, her hips were naturally narrow. On some worlds girls of her age already had children and on others they'd barely begun their education.

She was unmarried and no one, absolutely no one, had ever tried to make her learn anything; but she had a brain, guts, synthetic sinews and her own reason for being there.

In the end, Tris decided her only hope was to wait until the river stopped rushing in and the water level inside and outside equalized, so that was what she did. And maybe she should have used those long seconds to look for useful tools or find a dagger, but something else had occurred to her.

Digging around inside the table, Tris identified where the marble had been and felt with her fingers, shrinking back when something wet and bristling brushed against her skin.

"Oh, fuck it." Grabbing the marble from her pocket, Tris gave the thing to the tendrils, feeling them suck the marble from her grip. The AI wasn't nearly as non-bio as it claimed.

"Well, am I glad to be--" Whatever All Tomorrow's Parties had been about to say stuttered to a halt. Lights came on all across the cabin and half of them promptly blew, mostly the half which happened to be underwater.

"Good," Tris said, "you're--"

"Fucked," said the yacht. "Unless you unplug me now."

"I need you to work." Tris tried to sound commanding, only her voice came out small and rather uncertain. "I can't do this on my own."

"You should have thought about that," said the yacht, "before you stole me."

"But once I stole you," Tris said, "I wasn't on my own, was I? Because then I was with you." She thought about it. "Anyway," she said, "don't semiAIs have rules about having to protect the sentient?"

"That's household appliances," said the yacht, "and it's ‘not harm’ rather than protect. There's a difference."

The water was up to Tris's hips now, pulling at the bottom of her stolen leather jacket. She could feel the cold eating at her legs and dissolving all feeling below her waist. And the yacht was beginning to lean. Last time Tris had checked the cabin was level, ripped by currents and still filling with water but definitely level.

Now it slanted, with one side wall almost underwater and the other, the one with the door, almost clear. Only waves kept spilling in over the sill as the yacht began to settle.

"I'm going to die," said Tris. Mostly she was trying the idea for size, wondering if it was one she could accept.

"So?" said the yacht. "You should have played it differently. Besides, I'm the one who's really going to die. You're just going to revert to a previous back-up. What will you have lost, twenty-four hours? Forty-eight, if you're really careless."

"You don't get it," said Tris. "I don't have back-up." She thought it through, facing the conclusion. "When I die," she said, "I die."

She could almost hear the yacht's surprise. Well, the surprise of its AI, which was actually a blue marble matched to an axion-rich anemone. It wasn't quite sound and it wasn't really silence, more like a stumble in her head.

"You die if you get wet?" she asked the marble.

Her question amused it and the answer was no. It died if it got left behind, removed from a source of power and never found again. "Worry about yourself," suggested the yacht. "Why did you wake me?"

"I wanted to know where I am," she said.

"Where you wanted to be," the yacht said. "You're on Rapture."

"I know that," said Tris. "Where on Rapture?"

"In a river."

Tris sighed. "I'm going to take you out again," she said, "so you probably need to turn off the rainbow."

"Rainbow?"

"Those colours," said Tris. "The ones wrapped around you."

"You can see them?"

"Of course I can," Tris said. "If I couldn't see them I couldn't tell you they were there, could I?"

"Such a child," said the AI. "So empirical."

"Whatever. You want to tell me which river?"

"This one," said the yacht, and before Tris could kick the table, a ghost landscape hung in the air before her. It was topologically accurate, impressive and detailed in the extreme but it was skew to the lapping water and not at all what Tris wanted.

"Just tell me."

"Here," said the AI. "You're here." A tiny blue thread on the face of the ghost world lit red. At the same time, the world tilted slightly until it was out of true with the wall of the cabin but level over the water.

"And the Forbidden City?"

A different sector lit gold, and even without knowing the scale Tris could see that they were a long way apart.