In front stretched a dirty shag pile of wind-chopped water. As the boat chugged deeper into Phang Nga Bay, colour began to seep into the distant cardboard cutouts. Trees, a violent green, oozed puss-like from steep cliffs, a scraggy mass of cream and black. In places, where the water tickled, the rocks parted to reveal a flash of golden beach.But there was more to the islands than their good looks. In 1989, John Gray, an American, Welshman Simon Warren and Thai Soonthorn Sagulsan canoed into the mouth of a cave and, at the end of a long, dark tunnel, emerged blinking into a vast, open-air lagoon at the centre of the island. "It was like going back in time a million years," Simon had told me. There were giant fruit bats hanging from the cliffs, and monkeys. We must have been the first Europeans in there."The men quickly discovered that timing was critical.

The area has the third highest tidal range in the world (10 feet), making the caves only accessible at certain periods of the day, some only at full moon. Six months later, they formed Sea Canoe Thailand, offering trips to around a dozen of the bay's 150-odd islands.After a safety talk, we were given life jackets and climbed off the boat into a yellow inflatable canoe. Our Thai guide, Shore, sat at the back and paddled towards Phanak island. We slipped into the mouth of a cave, and, once the light had been swallowed, Shore shone a torch on to the rocks above us, illuminating a Disney-style, twinkling mass of stalactites that hung suspended like a frozen fountain.Paddling towards a jigsaw piece of light in the distance, we emerged back into daylight. We were in the centre of the island on a silent pond, the colour of green marble dusty with footprints. Out of the cliffs, which climbed to 100 feet around us, skinny trees grew at 90-degree angles, craning towards the sunlight. In one corner of the lagoon, a mangrove tree stretched its spaghetti roots into the water.

Cicadas made their din in surround sound, resembling fishing reels being turned at deafening speed. We drifted in awe, taking in the stillness.Shore paddled back through the tunnel and we headed for the next island, Nok Koom. On the way, we dragged our feet in the warm water while Shore sang us a Thai folk song. A kingfisher skidded past, giving us a flash of his ginger belly. The canoe squeaked perilously as it squeezed its way through a narrow tunnel, accompanied by our prayers that it wouldn't pop. Once inside, we glided into a cave, where torchlight revealed a stalactite the shape of a thundering organ.