All above me, the sky is positively bursting with stars. There are thousands and thousands more than I could ever see on the clearest night back home in Gloucestershire. My God, Gloucestershire — it feels so very, very long ago.

Over to the northern end of the small bay is a church. It’s packed to the rafters with the women of the village, and the lights from the windows dance on the water. A hymn drifts over the waves: it’s Onward Christian Soldiers. The words blend with the sound of the gentle swell lapping on the broken stone wall that keeps the sea off the road. From the southern end of the bay comes a deeper, brassy sound.

A bare-chested villager is standing in the back of a battered white pick-up truck, both hands cupped round the thin end of a conch shell. As he blows, men wander down from the rum shacks and surround the truck. The conch is a signal that the villager has landed a big fish and wants to cash in. His sinewy left arm hacks the large marlin into hunks that he exchanges for East Caribbean dollars.

And then we dive. I take a spontaneous gulp of air from my regulator and sink silently into the dark womb of the bay. For a fleeting moment, I feel uncomfortable as I’m swallowed whole by the paralysing blackness of the water.

I fumble for the catch of my torch and flip it on. I relax. I’m flying. I’m an aquanaut in liquid space, soaring over an alien world. The colours are almost unreal. I’m wearing a red filter over my mask that replaces the colours that are lost in normal under- water vision. I’m descending past pinks and reds, deep, deep reds, yellows, purples — it’s like swimming in a kaleidoscope.

As I reach the base of the patchwork coral wall, I spot a 6ft-wide area of virgin white sand. I plonk my natty pink fins down and take stock of where I am. The only sound is the yogic breathing of my regulator. I become transfixed by my own rhythms: in ... out ... in ... out... slowly ... long breath. I feel like meditating; maybe this is meditation? Oh, no, am I becoming a hippie?

My friend Kaj lands next to me and gives me the quizzical “everything okay?” sign, his thumb and index finger curled into a ball. I indicate that everything is very, very okay. In fact, I don’t think that I’ve ever felt more alive. He points to my torch and makes a throat- cutting sign. He wants me to turn it off. I’m completely going with the flow by now, and I flick the switch. We’re both plunged into darkness, and I can feel Kaj’s hand grab mine as he tries to steady us in our current position.

As my eyes adjust to the nothingness, I’m suddenly aware of being surrounded by thousands and thousands of tiny little points of light. The biolumin-escence in the water mirrors the star-packed sky above and I feel like I’m at the very centre of the universe. What the hell am I doing? Sitting on the Caribbean Sea floor, 60ft down, holding a man’s hand, watching a light show put on by a troupe of amateur algae? Let’s rewind.

I’D KNOWN Kaj since we were teenagers. We went to pubs together, hung out in the same crowd and became really close friends. Most of us went to university, then did the world-travelling thing before starting to settle down and trying to work out just what the hell we were going to do with our lives. Kaj did it all backwards. He didn’t “do” university. He was a computer whizz, and went and got a proper, well-paid, grown-up job in the City. Then, just as everyone started to settle down and couple up, Kaj left his job and went off round the world. That was about eight years ago. He still hasn’t come back.

About a year ago, through the magic of Skype, we got back in regular contact. He was now a scuba-diving instructor in the northeast of Dominica. All I knew about the Dominican Republic was that it was a tourist-infested ... “No, no,” said Kaj, this was the Commonwealth of Dominica, in the Lesser Antilles, known throughout the Caribbean as “the Nature Isle”. It is that very rare thing, an unspoilt Caribbean island: vast swathes of it are covered in ancient rainforest that has changed little since Columbus first saw and named the island in 1493.

Kaj assured me that it was one of the diving world’s best-kept secrets, and, as a little bonus, they were currently filming Pirates of the Caribbean 2 and 3 on his sleepy little island, so there was more action than usual.

I have to admit that I loathe the Caribbean. Posters showing blue skies and azure sea never tell you the truth: that it normally rains for three hours a day, the sea is as warm as a bath and you have to share it with glass-bottomed boats full of fat-bottomed, vomiting tourists. All this to the hideous backbeat of some two-bit steel-drum calypso. Oh, and Michael Winner goes there.

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