Tikehau - Isle of sky

The ring of Tikehau atoll forms an enchanted circle in the South Pacific Ocean, teeming with fish and seabird life. GRAEME LAY explores its marvels.

Captain Cook didn't like atolls. Neither did the other 18th-century European explorers who tacked across the South Pacific in search of new lands. Atolls - coral islands just a few metres above sea level - were virtually invisible from a sailing ship. Until it was too late and the ship's hull was holed by the reef.

The largest collection of atolls in the South Pacific is the Tuamotu group, named by those 18th-century voyagers the Dangerous Archipelago. The chances of striking one and foundering were strong. There are 76 islands in the Tuamotus, scattered like a galaxy across more than 20,000 sq km of ocean.

Today those atolls have been tamed. Several have airstrips, most are just an hour's flight from Tahiti. Their traditional cash crop, copra, has been replaced by tourism.

The lagoon of one atoll, Manihi, is the main source of the alluring black pearls which are sold in Papeete's fashion boutiques. Another, Rangiroa, is famed by scuba divers for its passes and the lagoon where it's possible to swim alongside hammerhead sharks and giant manta rays.

It was Charles Darwin, passing through in HMS Beagle in 1835, who first postulated that the atolls were remnants of ancient volcanoes, eroded and sunk almost to sea level over millions of years.

The lagoons vary in size: Rangiroa is so huge that it's not possible to see the motus (small islands) on its other side; neighbouring Tikehau is much smaller, being only 24km across. And it is Tikehau, with a population of 400, which is the latest island to provide hotel accommodation for visitors wishing to experience the uniquely beautiful environment of a South Pacific atoll.

From the air, Tikehau atoll appears dramatically in the dark blue ocean: a coronet of coral enclosing an opalesque lagoon. The largest motu, Tuherahera, contains the airstrip and the only village of any size.

The dozens of other motus are mere crumbs of sand and rock, but together they form an almost perfect hoop broken only by one passage - the Passe de Tuheiava.

Tuherahera has dazzling white sand roads, thickets of palms and shrubs with ember-bright blooms of bougainvillea, hibiscus and frangipani. Neat modern houses peer from the foliage, children race each other on bikes and lean dogs trot by.

On an atoll, motor vehicles are almost superfluous. Nearly everything moves by water. The Pearl Beach Tikehau Resort is on another motu, Tavania - a motor launch from Tuherahera's pier gets you across. This provides a suitable entree to atoll life.

Travelling across the lightly scuffed water of the lagoon under a blindingly blue sky, the sense of light and space is overpowering. All seems water and sky, the motus are almost invisible, their palm trees appearing to sprout straight from the water as they incline their crowns towards the lagoon.

Tikehau's newly minted hotel consists of a series of beachside fares and a string of overwater bungalows which straddle the lagoon like mop-topped wading birds. Each overwater bungalow has a panel of glass in its floor, so marine life can be seen without the inconvenience of moving outside. It's like watching a nature documentary on TV, except that it's real, mesmerising, and there are no commercials.

Sliding into the water in a channel between two motus, I'm quickly eyeballed by several fish in brilliant livery. Sinuous reef sharks cruise about, unafraid and unfrightening and an octopus backs away shyly, changing its marbled hues from orange to grey in an instant. These can all be seen with just the aid of a mask and snorkel. For a scuba diver, Tikehau must be a Mecca.

We are taken by launch across to Tuheiava pass, the atoll's only egress to the surrounding ocean, where there are shoals of barracuda, tuna, turtles, rays and gray and white-tipped sharks.

Elaborately constructed fish traps on either side of the passage snare hundreds of fish every day, which are collected and dispatched by air the same day to Papeete's market.

Back inside the lagoon, alongside a coral outcrop, is Tikehau's "lagoonarium". It's a wire pen in which many species of marine life have been detained for the visitors' pleasure: small fish of all kinds, a gang of sand sharks, a squadron of manta rays and several turtles. Here you can have the fish feed out of your hand - on fish caught and killed minutes earlier.

You can also enjoy poisson cru - raw fish dipped in savoury sauce - before you go snorkelling with the fish that might be on your plate tomorrow. But after a while the novelty of this wears off and is replaced by feelings of pity.

Fish, being largely brainless, don't mind. But to look underwater at the lovely turtles, banging their beaks against the wire and staring longingly at the lagoon on the other side, makes you realise that the lagoonarium is really a fish prison.

One day I hope the turtles will storm their Bastille and liberate themselves. There are so many free fish in the lagoon that can so easily be observed with a mask and snorkel, why incarcerate any? This is just pandering to tourist laziness.

But not all the wildlife is underwater. Tikehau's motus are also home to a huge variety of sea birds, none of them pinioned. Imperious frigatebirds, the condors of the Pacific, glide singly above the lagoon, while below them flocks of terns wheel and dive for fish.

A rewarding excursion on Tikehau is to a small island of fossilised coral far out in the lagoon, L'Isle aux Oiseau, a breeding sanctuary for thousands of birds, particularly red-footed gannets and brown noddies.

It's a marvellous experience to walk through the foliage on the little island, the sky teeming with wheeling birds, the branches of the shrubs and bushes filled with nests and fledglings, completely unperturbed by the human presence.

Atolls are special places, none more so than lovely, tranquil Tikehau. Its motus - uninhabited islets - are ideal for beachcombing or flopping about under a baking sky.

But it is the lagoon which entrances, with its lucent waters, shoals of fish and wheeling seabirds. To be out on its waters is like being in the centre of a beautiful lake.

Sea and sky merge in gradations of brilliant blue, the tops of the coconut palms on the surrounding motus are just visible on the horizon, connected by slivers of brilliant white sand, the specks of land and the expanse of water soothed by the soft trade wind from the south-east.

Captain Cook didn't know what he was missing.