It took them several minutes to get it away from the smooth area and out of the light. I supposed this was all they’d bother to do, but I was wrong. With the tent roof out of danger they moved around and began pushing the load in the direction the girl went after finding it.

This might be a nuisance. Maybe they just wanted it for a souvenir, but maybe they wanted to make a really close examination under better conditions — better light, or maybe even out of water. Whichever of these might be true, as long as they were interested someone was likely to notice the tank attachments. I’d have been much happier if they’d simply pushed the bow section off their roof and forgotten it. Now I had no excuse for not following them. Come to think of it, I should try to locate the entrance, or one of the entrances, to the place anyway.

They weren’t swimming fast, but they went a lot faster than I could roll the tank. Once again I wished that some real provision for moving the thing had been made, but the argument had been that the closer the whole rig got to being a submarine, the harder it was going to be to camouflage. I hadn’t bought the argument completely at the time, and I would have been even more delighted at a chance to reopen it now. All I could do, though, was hope the chance would come later on, and in the meantime wait until the swimmers got their burden a reasonable distance away and then start rolling in the same direction.

Perhaps I haven’t made clear quite all the nuisances involved in rolling the tank. The principle ought to be plain enough; it was simply a matter of letting the appropriate spring push out a leg against the bottom, on the side I wanted to go away from. It may not have crossed your mind that this general method of getting around meant that living equipment, control panels, and other fixed gear were some-

times to one side of me, sometimes to another, and sometimes above or below. There were times when it was very hard to keep from sitting on all the leg-control buttons at once, for example. As I’ve said, the legs were meant more for position and altitude fine control, and to keep the tank from rolling on a slope, than for genuine travel. The need for the latter had not been foreseen, or at least hadn’t been considered very great, by the authorities.

At least, concentrating on working the machine along the bottom kept my mind from the worries I’d felt on the way down. It was actually more likely now that I’d come under unfriendly observation, but at least I wasn’t brooding over it. The swimmers had vanished in the distance, nothing else could be seen moving in the lighted area to my left, and nothing at all could be seen the other way. The bottom under the tank couldn’t be made out in detail, and in a way I was groping along — though the verb isn’t exactly right, since it implies that you can feel what’s ahead of you. I couldn’t feel anything; I could only note whether my vehicle rolled a little way, a longer way, or not at all whenever another leg was extended. When it didn’t roll at all I had to guess which other legs to try. It would have been a lot easier if I had dared to use enough light of my own to get a decent sight of the bottom, but I wasn’t that silly. If the local population included swimmers, I didn’t have a prayer of knowing when any of them were around; when this mess had started we were thinking of subs and sonar. These I was ready to spot.

The slope was not very regular, as I quickly found. Twice I rolled forward out of control for several yards when I reached a small dip. Once I thought I was stuck for good — I couldn’t go forward, back, or what was presumably downhill toward the light. As a last resort I tried uphill and found that it wasn’t uphill at all; I rolled out of control again into a hollow where I couldn’t see the lighted area except as a vague, diffused glow over the ridge I’d just crossed. Getting out of that hollow used a lot of time and an irritating amount of stored power.

I couldn’t even relieve my feelings with language. The coupling from air through plastic to water, and from water through helmets to gas and human ears, may be pretty bad, but it isn’t zero; and the sound-transmitting properties of cold water make up for a lot of matching deficiencies. I didn’t dare say a word.

Once out of that devil-invented gully I stopped, once more in full sight of the tent roof and tried to take stock.

My power was rather low. There was no way of telling whether I might reach the entrance in three hundred yards or three thousand; the former seemed more likely, since the girl hadn’t taken too long to come back with her help, but then she might have met the men already outside. Nothing was certain enough to give any possible line of action even the dignity of a calculated risk. It wasn’t possible to calculate.

I had to find out more, though. I’d cooled down a little from my original reaction — I could believe what I’d seen, and I realized that others would, too — but the news I had wasn’t as helpful as it was supposed to be to the Board. If a police unit were to do anything but grope around, it should know where to start. A regular entrance would make a logical place. Of course it wasn’t likely that the tent roof would really keep a sub out; but judging by the area the tent enclosed, the chances of breaking through at a strategically useful point would be rather slim.

Maybe the best thing to do would be to throw out the caution policy and turn on my lights. The extra power would be offset by more efficient travel when I could see where I was going and I should stand a better chance of reaching the entrance before my juice failed entirely and automatically let my ballast go. If I were seen, no doubt some of the swimmers would come close enough to give me a really good look, so I might get a better idea of their high-pressure technique before I left.

I’m a cautious man by nature, and thought that one over for quite a while before I bought it. There was plenty against it, of course. Just because all I’d seen was swimmers rather than subs didn’t prove there weren’t any subs. If there were, there would be an excellent chance that I could never get back to the surface — but I’d accepted that risk before starting the trip. I ping-ponged the matter for several minutes. Then I took a good, deep breath on the theory that I might not get many more and turned on one of my spots.

It made a difference, all right. The bottom was mostly rock, as I’d suspected, and was very rough — no wonder I’d had trouble using my legs effectively. Able to watch what I was doing, I resumed travel and, as I’d hoped, made much better speed with much less power drain. It wasn’t exactly easy yet; I was still rolling, and had to change lights as well as legs as I rolled, but the improvement was encouraging.

I could see more motion around me. There was a lot of small life — shrimps and their relatives — that I hadn’t been able to spot before. They got out of my way without being too distracting. There were also plantlike growths, though considering how far they were from the nearest natural light it seemed likely that they were sponges or something of that sort. They neither helped nor hampered the rolling, as far as I could tell.

However, I was paying for the much better short-range vision with a much worse view of distant objects. I might have been surprised quite easily by a group of swimmers, but what actually happened was less predictable. I lost orientation.

Not in the compass-direction sense and not completely. I could still see the lighted area to my left, though not as well as before; my compass still worked, when it happened to be right side up; but my sense of up and down, depending more on my view of a few square yards of ocean bottom than on my semicircular canals, was fooled when some of the bottom ceased to be horizontal.

The change must have been gradual, or I’d have spotted it within the small area I could see well. As it was, I overlooked it completely; suddenly I was on an area of rock sloping much more steeply than any I had traversed up to then. Before I knew it the tank had started a stately roll to the left; after I knew it, leg after leg poked out in that general direction proved useless.