It was Ian who had called the previous evening. He was in charge of all the diving stuff on Hayman, and a more helpful and friendly person would be hard to imagine. We got the Sub Bug unpacked, and examined it as it stood gleaming in the sun.

It is, as I have said, shaped like the front half of a dolphin. The body of it is blue, and toward the front there are two small yellow fins, one on each side, that can rotate through a few degrees and direct the Sub Bug upward or downward. At the back are two large handles that you hold on to as the Sub Bug pulls you through the water. Within reach of your thumbs are buttons that make the thing go, and control its ascent and descent. Inside the Bug is a cylinder of compressed air—a normal scuba cylinder—and this provides power to spin the two propellers that push the Bug forward, and also supplies air down a flexible tube to a free-floating regulator. A regulator is the thing you stick in your mouth that gives you your air when you’re diving. The point of this arrangement is that you only need your mask and flippers; you don’t need to carry a scuba tank on your own back, because you’re getting your air direct from the Sub Bug. The Bug is designed in such a way that you can set a maximum depth beyond which it will not go. The very maximum anyway is thirty feet.

Ian had received a flurry of faxes from Martin Pemberton about setting up the machine, and was pretty confident about it.

“No worries at all,” he said, and asked me what I planned.

I said it might be an idea to take it for a shallow local try out before taking it out into deep water.

“No worries,” he said.

I said that we could then take it with us on the proper diving expedition that was going out from the island the following morning.

“No worries,” he said.

“So I will then spend a little time trying it out, getting used to it, and putting it through its paces around the reef.”

“No worries,” he said.

“And then, er,” I said, “for the purposes of this article I have to write, which is by way of being a sort of comparative test drive, I want to try the same thing on a manta ray.”

“No chance,” he said. “No chance at all.”

I suppose I should have foreseen this.

Or perhaps it was just as well that I hadn’t foreseen it. If I had foreseen it, I wouldn’t have been standing there half in a wet suit looking out at the glittering Tasman Sea and thinking, “Oh damn.” I would have been sitting fiddling in my office in Islington wondering if I’d done enough “work” yet to justify going out and getting a bun.

The issue was very simple. As someone who has spent over two years working on ecological projects, the very first thing I should have realised was that you don’t disturb the animals. It might have been all right to try and mount a manta ray ten years ago when I first heard about it, but not now. No way. You don’t touch the reef. You don’t take anything. No shells, no coral. You don’t touch the fish, except maybe a few that it’s okay to feed. And you certainly don’t fuck about trying to ride manta rays.

“Hardly any chance you’d even be able to get near one anyway,” said Ian. “They’re very timid creatures. I guess some people have managed to get to ride on a ray in the past, but I would imagine it would be very difficult. But now we just can’t allow it.”

“No,” I said, rather shamefacedly. “I understand, believe me. I just hadn’t really thought it through, I guess.”

“But we can go and have some fun with the Sub Bug,” said Ian. “No worries. We can take some pictures too. That’s a hell of a camera you’ve got there.”

We now come to another rather embarrassing part of the story about which I have so far been extremely silent. Some very nice people at Nikon in England had lent me for this trip brand-new Nikonos AF SR underwater autofocus camera, which is about £15,000 worth of the most sexy and desirable and fabulous camera equipment in the world. The camera is just wonderful, brilliant technology. Really. You want to take a photograph underwater, this is the perfect thing. It’s an astounding bit of kit. Why am I going on about it like this? Well, I spend a lot of time working on a computer, and because I am used to using a Macintosh, I hardly even bother to read manuals and so—I didn’t really bother to read the manual for this camera.

I realised that when I got the films back.

Please—I really don’t want to say any more, except to say thank you very much, Nikon. It really is an awesome camera and I hope very much that you will let me borrow it again one day. I won’t mention the camera again in this article.

We took a small dinghy out to a tiny deserted island about ten minutes away. Ian and I spent a happy hour or so pootling around with the Bug. We dealt with a couple of problems—a grain of sand in a valve, and so on. We worked out that the Bug didn’t work too well in very shallow water when it had to work against a tide. Well, we’d take it deeper tomorrow. Jane lay in the sun on the beach and read a book. After a while we got back in the dinghy and went back to Hayman. Not much of a story in all that, I suppose, but the reason I mention it is that I remember it very vividly, and one of the shortcomings, I sometimes feel, of somewhere like, for instance, Islington, is the lack of any immediately accessible tiny islands that you can spend the afternoon pootling around with Sub Bugs on. Just a bit of a poignant thought, really. We don’t even have any decent bridges you can deface.

There were about ten of us on the dive boat the following morning. The hotel is so spacious and rambling that you don’t often get to see many of the other guests, but it was interesting to begin to realise how many of them were Japanese. Not only Japanese, but Japanese who held hands and gazed into each other’s eyes a lot. Hayman, we discovered, was a major Japanese honeymoon destination.

The Sub Bug sat up on the back of the boat, and I sat looking at it as we made the hour’s journey out to the reef. Hardly any of the Barrier Reef islands are actually on the reef itself, except for Heron Island. You have to get there by boat. I was very excited. Apart from a couple of refresher dives in pools, this was my first proper scuba dive in years. I absolutely love it. I’m one of those people who has been tantalised by the flying dream for years, and scuba diving is the closest thing I know to flying. And for someone who is six foot five and less sylphlike than, to pick a name at random, the Princess of Wales, the sensation of weightlessness is an ecstatic one. Also, I usually vomit on the way back, which is a good way of working up an appetite.

We reached the reef, moored, got into our wet-suit gear, and prepared to dive. At low tide, the reef usually breaks the surface of the water. You can even walk on it, though that is now discouraged because of the damage it can cause. Even when the tide is high, though, reef diving is not a deep-diving sport. Most of what there is to see lies in the upper thirty feet, and there’s rarely any cause to go deeper than sixty feet. The very deepest a sports diver can go is about ninety feet, but there’s really not a lot of point. You’re usually looking at bare rock rather than coral at that depth, and Boyle’s law means that you use up your air much faster down there. Also, you have to spend much more time on the surface between dives if you’re not going to get the bends. The Sub Bug keeps you at a safe maximum depth of thirty feet.

I wanted to do a regular dive first to get my bearings. Two at a time, we clamped our masks and regulators to our faces did the Big Stride off the diving deck at the back of the boat; and dropped into the water in an eruption of bubbles. A moored dive boat always attracts the attention of a lot of local fish who expect, usually rightly, that they will get fed. The ones you’ll get to see if you’re lucky are the Maori wrasses, which are extraordinary pale olive-green creatures about the size of a Samsonite suitcase. They have large, protuberant mouths and very heavy protuberant brows, but the reason for the name Maori, an Australian will assure you apologetically, is some paintlike markings on their brow. Australians are not racists anymore.

There were quite a few wrasses around the boat, and I made the mistake of getting between a couple of them and some pieces of bread that someone had thrown from the boat. The animals blithely barged past me to get at the food.

I sank down to the reef in the huge space of water and light beneath the boat, and drifted easily round it for a while to get used to being underwater again, then came back to the boat to divest myself of my scuba tank and collect the Sub Bug. Together, Ian and I hauled it into the water. I got myself into position behind the thing, and started it up. One of the curious features of scuba diving is that your suit and equipment seem so heavy and cumbersome and unwieldy on the surface—which is one of the things that tend to frighten beginners—but once you descend below water level, everything begins to flow smoothly and easily, and the trick is to exert yourself absolutely as little as possible, in order to conserve oxygen. It is, almost by definition, the least aerobic sport there is. It won’t make you fit.

At first I was disappointed that the Sub Bug wouldn’t move me faster than I could swim. We were gently pulling our way down, but as I started to get used once more to the slowness with which everything happens underwater, I began to relish the long, slow, balletic curves it let you make through the water, stretched out at full length behind it instead of swimming in the normal position with your arms by your side or on your chest. Following the contours of the reef became like skiing in ultra slow motion—an almost Zenlike idea. I began to enjoy it a lot, though after fifteen minutes of experimenting with it, I began to feel I had exhausted its repertoire and began to look forward to swimming under my own power again. I suspect that it’s probably a machine best suited to people who want to experience a dive but don’t want to bother with the business of learning to use buoyancy jackets and so on.

I returned to the boat and we hauled the thing back up out of the water. Well, I’d driven the Sub Bug. But over lunch I was worried about the total collapse of my absurd comparative test-drive plan, and discussed my thoughts with Ian and Jane.

“I think we just have to think about the comparative test drive on a kind of conceptual basis,” I said. “And we have to award some points. Obviously the Sub Bug wins some points for being portable up to a point. You can take it on a plane, which you wouldn’t do with a manta ray, or at least not with a manta ray you liked, and I think that we probably like all manta rays on principle really, don’t we? Your manta ray is going to be a lot faster and more manoeuvrable, and you don’t need to change its tank every twenty minutes. But the big points that the Sub Bug wins are for the fact that you can actually get on it. I think it has to get a lot of credit for that, if you’re thinking of it as transport. But then, let’s turn the whole thing around again. The reason you can’t actually ride a manta ray is a sound ecological one, and on just about every ecological criterion the manta ray wins hands down. In fact, any form of transport that you can’t actually use would be a major ecological benefit, don’t you think?”

Ian nodded understandingly.

“Can I get on and read my book now, please?” said Jane.

For the afternoon dive, Ian said he wanted to take me in a different direction from the boat. I asked him why, and he looked noncommittal. I followed him down into the water and slowly we flippered our way across to a new part of the reef. When we reached it, the flat top of the reef was about four feet below the surface, and the sunlight dappled gently over the extraordinary shapes and colours of the brain coral, the antler coral, the sea ferns and anemones. The stuff you see beneath the water often, seems like a wild parody of the stuff you see above it. I remember the thought I had when first I dived on the Barrier Reef year ago, which was that this was all the stuff that people used to have on their mantelpieces in the fifties. It took me a while to rid myself of the notion that the reef was a load of kitsch.

I’ve never learnt the names of a lot of fish. I always swot them up on the boat and forget them a week later. But watching the breathtaking variety of shape and movement keeps me entranced for hours, or would if the oxygen allowed. If I were not an atheist, I think I would have to be a Catholic because if it wasn’t the forces of natural selection that designed fish, it must have been an Italian.

I was moving forward slowly in the shallows. A few feet in front of me the reef gradually dipped down into a broad valley. The valley floor was wide and dark and flat. Ian was directing my attention toward it. I didn’t know why. There seemed to be just an absence of interesting coral. And then, as I looked, the whole black floor of the valley slowly lifted upward and started gently to waft its way away from us. As it moved, its edges were rippling softly and I could see that underneath it was pure white. I was transfixed by the realisation that what I was looking at was an eight-foot-wide giant manta ray.

It banked away in a wide, sweeping turn in the deeper water. It seemed to be moving breathtakingly slowly, and I was desperate to keep up with it. I came down the side of the reef to follow it. Ian motioned me not to alarm the creature, but just move slowly. I had quickly realised that its size was deceptive and it was moving much more swiftly than I realised. It banked again round the contour of the reef, and I began to see its shape more clearly. It was very roughly diamond-shaped. Its tail is not long, like a sting ray’s. The most extraordinary thing is its head. Where you would expect its head to be, it’s almost as if something has taken a bite out of it instead. From the two forward points—the outer edges of the “bite,” if you see what I mean—depend two horns, folded downward. And on each of these horns is a single large black eye.

As it moved, shimmering and undulating its giant wings, folding itself through the water, I felt that I was looking at the single most beautiful and unearthly thing I had ever seen in my life. Some people have described them as looking like living stealth bombers, but it is an evil image to apply to a creature so majestic, fluid, and benign.

I followed it as it swam around the outside of the reef, I couldn’t follow fast or well, but it was making such wide, sweeping turns that I only had to move relatively short distances round the reef to keep it in sight. Twice, even three times it circled round the reef and then at last it disappeared and I thought I had lost it for good. I stopped and looked around. No. It had definitely gone. I was saddened, but exhilarated with wonder at what I had seen. Then I became aware of a shadow moving on the sea floor at the periphery of my vision. I looked up, unprepared for what I then saw.

The manta ray soared over the top of the reef above me, only this time it had two more in its wake behind it. Together the three vast creatures, moving in perfect, undulating harmony of line, as if following invisible rollercoaster rails, sped off and away till they were lost at last in the darkening distance of the water.

I was very quiet that evening as we packed the Sub Bug back into its big silver box. I thanked Ian for finding the manta rays. I said I understood about not riding them.

“Ah, no worries, mate,” he said. “No worries at all.”