The next few hours were some of the happiest Marine Boy could remember. Jack was brilliant company, and said "Cool" and "Wow" a lot. Marine Boy showed him the engines and explained how Ocean Base was, in effect, the largest submarine ever built. Jack was awed by the massive drive shafts – even though they were at rest – and was gratified by the way the engineering crew tolerated him sticking his nose into everything. They visited the nuclear reactor that provided Ocean Base's power – or at least the control room that regulated it. They visited the main bridge, the navigation room and the hydroponics farms. Jack was immensely impressed when Marine Boy showed him the banks of torpedo tubes ("For self-defence only") and the maintenance bays for the Patrol Craft and other submersibles. A small remote-controlled drone was being tested, and a technician good-naturedly vacated his seat so that Jack could pilot the machine through the depths ("It's like a computer game, only real!"). They visited the huge fish tanks where there swarmed uncounted species, and the plankton labs, where they were working on the process for producing pure protein.

"You mean in the future we'll all just pop a little green pill instead of having dinner?"

"Not quite. It's more that they'll shortly be able to use this stuff to make any food you want – from steak to chocolate. Or something like that; it'll be a while before it's perfected. I have trouble getting my head around it, to be frank."

"In which case, I don't stand a chance."

"Oh I don't know – you seem pretty smart to me."

"Not compared to you."

"How do you mean?"

"Oh come on... Well for a start, I glanced at that piece of your homework I picked up. Chemistry, I think, but it might as well have been in Egyptian Hiero-wossnames for all I could tell. But that's just for starters. Here we are on the most advanced piece of technology on the whole damn planet; and you not only live here, you understand it all."

"I wouldn't go that far."

"You've been explaining it to me all morning."

"Just the fifty cents tour."

"Whatever. And on top of all that you're some sort of secret agent, always going on death-defying missions and that."

"I told you not to believe all that stuff."

"Yeah? Well I do. Johnny, you're my hero." Jack put his arm round Marine Boy's shoulders. Marine Boy responded by putting his arm round Jack's waist, and the two boys walked along, bickering about who was a hero and who wasn't.

Presently, they came to a door they'd not passed before. Jack read the sign on it, and stopped. "Gym?" he asked. "You have a gym down here?"

"Sure. Two, actually. Plus a bowling alley, a cinema, and a sort of nightclub."

"A nightclub?" Jack was incredulous.

"Well, a place that sort of serves as a nightclub. I don't go, usually."

"Why not?"

"Well, who would I dance with when I got there? Nurse Callaghan?" Jack pulled a face.

"Exactly," Marine Boy said. "Most of the older guys go there because that's where they can drink. I know Bullton does, anyway. Drinking anywhere else on Ocean base is strictly forbidden."

"That doesn't stop him carrying a bottle in his mini-sub."

"Yeah. I honestly didn't know about that. Er, what did it taste like, by the way?"

"The whisky? Foul. Trust me on this."

"Seemed to wake you up, though."

"Made me cough my guts up, more like. You've never tried it?"

"No."

"Tried any other sort of booze?"

"Beer a few times. Just a small glass. Wine once or twice – oh and I had about an egg-cup's worth of champagne when we had a ceremony to celebrate Ocean Base's second anniversary. That was on my thirteenth birthday as it happens."

"So you and this sub share a birthday?"

"Never thought of it like that, but yeah, I suppose."

"Cool. What's champagne like?"

"The bubbles got up my nose."

"I don't suppose you could lay your hands on some?"

"I'd be in a world of shit if I even tried."

"Yeah, sorry, dumb idea. But hang on – this place has a cinema as well?"

"A small one – maybe thirty seats. See, this place is a sort of self-contained village. People don't just work here, they live here, and no-one can leave very easily. So we have to have ways of keeping ourselves entertained. We've a library of films and TV shows and stuff. You can watch what you like any time on the screen in your cabin, but sometimes it's good to be part of an audience."

"Makes sense. So, you want to catch a movie tonight?"

"Sure would."

"Great. What are they showing?"

"Search me. They take requests sometimes, though."

"They do?"

"Why not? It's all in the central data banks anyway. All someone has to do is push a few buttons."

"I suppose. Say..." Jack suddenly looked embarrassed and stared at the floor. "Do they ever show any, you know... porn movies?"

"Er, Not on the big screen, as far as I know." Marine Boy felt just as embarrassed as Jack. "I'm pretty sure there are some in the data bank though. Like for private downloading and that, but I don't have the password. It's the only bit of the software I've not been able to crack." Marine Boy grinned apologetically, not least because this last had been a lie. The truth was that the R-rated download password was one of the few things he'd never tried to crack.

There was an awkward silence. "You, er, ever watch any porn?" Marine Boy asked Jack quietly, without looking him in the eye.

"Not really, no. Caught a ten-second glimpse of something once."

He didn't elaborate, and there was another awkward pause.

Eventually, Jack said, "Well anyway. Movie tonight. Action one for preference. But now, lets check out this gym." He pushed open the door. "Hey, that's pretty cool – a basketball court underwater. Wanna go one-on-one?"

"Love to."

Marine Boy found a ball and he and Jack began to hustle each other on the court. There was a sprinkling of other Ocean Base personnel in the gym, using the various exercise machines, but over the next few minutes, punctuated by cries of "Two points," and "Foul, dammit," they all drifted away so that Jack and Marine Boy had the gym to themselves. Neither noticed this.

Eventually, Marine Boy threw up his hands. "OK, I surrender. You can whip me at basketball."

"I'm taller. Gives me an advantage. What else is there?"

"Soccer?" Against one wall of the gym was a small five-a-side goal.

"OK: penalties. You go in goal first."

After ten penalties each, Marine Boy was leading by seven goals to four. "That one to you," Jack laughed. "Anyone ever tell you you're a bit of an acrobat?"

"When it comes down to it, swimming underwater and acrobatics aren't so different. It's all about balance." He turned a couple of casual cartwheels, then started walking on his hands towards the far end of the gym. As he did so, he looked back at Jack to see if he was impressed, and collided with a rowing-machine. He collapsed in a heap and Jack roared with laughter. Marine Boy joined in.

"Quite a lot of exercise machines," Jack remarked, courteously helping Marine Boy back to his feet.

"We're all supposed to keep fit while we're on board. Even Nurse Callaghan in theory, though I've never seen her in here."

"Ugh, what a thought," said Jack. "Still, you must work out quite a bit yourself. I mean, those are wicked abs." He placed his hand flat on Marine Boy's stomach. "Hard, too. You sure you're only thirteen?"

"And a half. You're not so bad yourself."

"Nah, I'm a bit skinny. I've grown three inches in the last year without putting on any weight. I feel sort of stretched. Hey, how much can you bench press?"

The boys lay on adjacent benches and matched each other lift for lift, gradually increasing the weight. Ocean Base had a fitness instructor – a former Navy man called Hutchinson – and though he usually left Marine Boy to his own devices, he had given him some stern lectures in the past. "I don't want to know," he'd said, "about your personal best. I want you to concentrate on building stamina, not one-off potential. Stamina is what counts out there. Find a weight you're comfortable with, and concentrate on doing as many reps as you can. Don't try to force yourself beyond your maximum – especially not while you're still growing."

After one painful attempt at 175 pounds, Marine Boy had heeded this advice. He could do twenty-five reps of 100 pounds, and a dozen of 120. In competition with Jack, however, he felt the need to push on. Surely he could manage 175 now, even if only once?

The boys progressed to 150 pounds. Marine Boy managed it with an effort, but felt that he could go further. From the grunting noises Jack was making, however, he seemed to be pretty close his limit. In his head, Marine Boy started to rehearse his attitude of magnanimous triumph.

"Ah, there you are, young man. Or young men, I should say."

Marine Boy looked up in horror. Nurse Callaghan was standing by the door of the gym, with her arms folded across her chest and a stern expression on her face.