And worse, far worse for my self-respect as a passingly sceptical citizen of the upper world, I actually marvelled over coral too. Precisely as if I’d just that very moment come screeching into the universe, I gasped at its variety, its prodigious size, its extraordinary forms and colours. We nudged our way through coral canyons, past infinite ravines and potholes gaping to eternity. We saw cliffs of mushrooms – fungia acitiniformis – staghorns, flower arrangements, bath sponges, and giant brains, like the spilled cranial innards of one whole year’s intake of Oxford and Cambridge put together. I found myself making noises like David Attenborough. ‘It’s a miracle of natural engineering and architecture,’ I said. ‘A testimony to nature’s most inventive builder and creator both – the tiny coral polyp.’ We sat, Ros and I, with our noses to the glass of the ersatz submarine, as fish-fixated, as reef-drunk, as Hans and Lottie Haas.

The idea even assailed me that I would like to be a scuba diver. I was a long way from home. Nobody need ever find out. I made enquiries as to the cost and duration of the course and was put off only when I learnt that you were expected to be able to swim first.

We were returned from the sub to the boat for a buffet lunch, prior to being dropped on Michaelmas Cay itself for the afternoon. We were a smaller and more intimate party now than the one that had left Cairns earlier in the day; some of those had stayed on Green Island or been whisked off to other reefs; we were now down to about thirty, most of us bent on some serious snorkelling.

I thought that for lunch people were in the main dressed too scantily. A beautiful but intensely solemn German girl glided between the tables of prawns and beetroot in nothing but three small triangles and a slave anklet in matching colours. Although she was only carrying a small plastic bag she was to produce five changes of triangle, together with appropriate slave anklets, before the day was out. An unfortunate American girl, with thick-lensed spectacles and protruding teeth, wore something that looked like a cut-down baby’s romper suit, which transgressed the bounds of what I think the women’s magazines mean by the bikini line. And the two male diving instructors who were superintending us had stripped down to tiny green pouches. Altogether, between the excrescences and the triangulations and the stubble, it was hard for either of us to know where to look. I was relieved when we were finally let onto the island so that I could stretch out face down on the beach, leave Ros to play with the fish, and go to sleep.