Travel: This place is a real dive: Scuba divers travel the globe looking for the ultimate plunge. Nick Hanna tries out some of the best

Astormy afternoon on a Caribbean beach, and I am standing with a bunch of despondent-looking scuba divers watching the breakers crashing over a reef on the west side of Little Cayman Island. Having travelled thousands of miles to get here, we are beginning to wonder if it has been worth it. We plunge in, anyway.

As I drift out through a gap in the reef and emerge on the ocean side, the panorama of the reef wall is laid out before me, an extravaganza of living colour with huge, blood-red sponges, corals and deep-water gorgonians crowding the drop-off. In among the canyons that gash the reef wall, an array of rainbow-coloured fish dart about, chasing and being chased in the never-ending cycle of reef predation. My spirits rise as I kick my fins and cruise alongside the reef wall, drifting past blue-green parrotfish chomping on the coral polyps, massive groupers lurking under ledges, and pairs of angelfish flitting about between the waving fronds.

There is always this moment of truth when diving somewhere new, as you sink beneath the waves to see what lies in store. This dive - and the others that followed - on Bloody Bay Wall on Little Cayman lived up to all my expectations. Here was a coral reef as it should be, the result of millions of years of creation in all its untouched glory.

Sadly, it is not always like this. All too often the scene is one of devastation, of smashed and broken corals littering the seabed, a grey, lifeless area where the few remaining fish dart nervously about, deprived of shelter and food. Sometimes this is the result of a natural catastrophe such as a hurricane, and reefs normally have a remarkable capacity to regenerate from such damage.

But now their ability to recover is being diminished by the continuous onslaught from human activities: sewage and toxic chemicals are pumped over them, silt from construction sites chokes them; soil run- off smothers them, and boat and cruise ship anchors smash them up. They are even bombed with explosives by fishermen desperate to increase their yields. And tourists, too, cause a lot of damage, either walking on the reefs or barging clumsily into them while diving and snorkelling.

Fortunately many countries that are dependent on marine tourism have implemented conservation policies and marine parks to preserve the exuberant wilderness of reef life. This has long been the case in the Cayman Islands, hence their popularity among divers. Elsewhere in the Caribbean, the remote Turks and Caicos islands have some superb reefs, the best of which are on West Caicos and Grand Turk. Often the most beautiful reefs are difficult or expensive to reach, but on Grand Turk, just a few hundred yards from the beach at Cockburn Town, lies one of the finest reef walls in the Caribbean.

Nine miles long and dropping more than 7,000ft into the Turks Island Passage, the reef is so close that within 20 minutes of finishing breakfast you are in the water, descending over a lush and fertile marine ecosystem. A straw poll of divers in my hotel, many of whom had travelled the globe in search of the ultimate dive, resulted in a unanimous vote for the Turks and Caicos as one of the best.

In the western Caribbean, the small Central American nation of Belize has a barrier reef running the length of the country that is rivalled only by Australia's for size and complexity, with huge areas of reef, seldom visited, that offer exciting opportunities for divers. The enormous diversity of hard and soft corals and the dazzling variety of reef fish are best appreciated by diving from one of the bases on the atolls (of which Belize has three out of only four in the western hemisphere) such as Lighthouse Reef or Glover's Reef. Another alternative is a live-aboard dive boat for access to even more of the beautiful and untouched reefs.

The Great Barrier Reef, built up by tiny coral polyps over thousands of years to create the largest living structure on the planet, has had its share of catastrophes (including the devastation of large areas by the crown- of-thorns starfish) but there is so much of it that it is not hard to find good diving. Stay clear of the reefs near Cairns, abused by too many novice divers. If you can afford it, take a live-aboard boat to the Coral Sea or, as a land-based option, Lizard Island, just 20km from the Outer Reef. A long-standing favourite with divers is Heron Island farther south.

The reefs of South-east Asia have suffered heavily from the pressures of development and population, but Sipadan Island off the east coast of Sabah in East Malaysia is a rare find, a small oceanic island sitting on top of a massive sea mountain extending some 600 metres down to the sea bed. Just a stone's throw from the beach, the pale, aquamarine waters over the sandy seabed change abruptly to deep blue where the reef wall begins.

The thriving reef exhibits a profusion of seafans, black coral and hard and soft corals inhabited by innumerable iridescent fish. Because of its position in mid-ocean, Sipadan also has large numbers of pelagic (open-water) species cruising the reef walls, with schools of barracuda, manta rays and hammerhead sharks congregating on the headlands. There are so many turtles that scarcely a dive goes by without seeing a dozen or more.

And so to the Red Sea, the most accessible and, many would say, the best coral reefs within reach of the UK. With the development of dive tourism in Egypt in recent years, an enormous number of options are now available, ranging from camping safaris down the Red Sea coast to a diving holiday in the comfortable surroundings of the new, Swiss-run Movenpick Hotel or the Hilton Fayrouz Village at Na'ama Bay near Sharm el Sheikh in southern Sinai.

Set against a backdrop of the scenic south Sinai mountains, Na'ama Bay is a resort with easy access to excellent dive sites along the coast and those offshore in the Straits of Tiran. It is also the most convenient base for the spectacular reefs at Ras Muhammad where, just a short distance from shore, the reef wall plunges 2,000 metres to the seabed. This dynamic environment is populated by more than 1,000 species of fish and a wealth of deep-water species - including the occasional whale shark.

On the other side of the Red Sea, one of the newest areas to be opened up is around Safaga, 60km south of the port of Hurghada. Within the vicinity of Safaga are numerous coral islands and underwater walls, overhangs and pinnacles inhabited by prolific marine species, including rays, barracuda, sharks and dolphin, with dive sites such as Panorama and Abu Kafan reefs - said to be as good as the fabled Ras Muhammad.

Nick Hanna is the author, with Sue Wells, of The Greenpeace Book of Coral Reefs (Blandford, pounds 16.99).

FACTFILE

MOST of the world's best diving spots are featured by the UK's leading diving holiday company, Twicker's World (081-892 8164). Packages (including diving) to the Cayman Islands start from around pounds 1000 for one week. Little Cayman can be reached on a day trip; if you want to stay on the island, the best place is the top-rated Pirate's Point Resort, with daily rates from around dollars 160 (pounds 110) fully inclusive (telephone and fax: 010 1 809 948 4210). Cayman Airways (071-581 9960) flies twice daily to Little Cayman for dollars 77 return.

In the Turks and Caicos the atmospheric Salt Raker Inn, just outside Cockburn Town on Grand Turk, is a long-time favourite with divers: packages through Twicker's World start from around pounds 1,500 for two weeks inclusive of diving. Eight days aboard the Sea Dancer, cruising the remote reefs of the Turks and Caicos, costs from pounds 1,704, also through Twicker's World.

In Belize, tailor-made itineraries to the atolls can be arranged through Reef and Rainforest Tours (071-381 2204); one week aboard a dive boat costs from pounds 960 (not including flights) through Traveller's Interests (071-287 1642). Conservation work holidays for divers on the Barrier Reef are organised by Coral Cay Conservation (071-498 6248); the cost is pounds 1,675 for 28 days, fully inclusive.

For Australia's Great Barrier Reef, a brochure covering resorts and reef cruises is available from the Oueensland Tourist and Travel Corporation (071-836 7242). Lizard Island costs pounds 2,361 for one week (not including flights to Australia) through Austravel (0272 277425), but it is one of Queensland's most exclusive resorts. Heron Island costs a more realistic pounds 490 per week (inclusive of diving but not flights) through Twicker's World.

Sipadan Island in Sabah, East Malaysia, can be booked direct through Borneo Divers (010 60 88 221550), with four days/three nights for dollars 770 fully inclusive from Kota Kinabalu, or through Twicker's World for an 11-day itinerary (seven on Sipadan) for pounds 1,498. Sipadan is also featured by a new dive holiday company, Scuba Safaris (071-498 0003). It specialises in some of the world's most exotic diving locations such as Cocos Islands (Costa Rica), Papua New Guinea, the Solomon Islands, Palau, the Galapagos (Ecuador), and tailor-made underwater photography trips.

There is enormous competition for Red Sea dive trips, which means costs can be reasonable. Twicker's has two weeks at the budget-priced Sanafir Hotel from pounds 359 (flights and accommodation; diving packages from pounds 280 for 13 days). The Hilton Fayrouz and the Movenpick cost from around pounds 700 on the same basis. Regal Diving (0353 778096) also features several hotels at Na'ama Bay. One of the most popular options has been the Explorer Safari down the Red Sea coast operated by Oonasdivers (0323 648924); covering 140km of deserted coral reef coastline from El Quesir down to Marsa Alam, the eight-day tour costs pounds 590 fully inclusive of flights, safari and diving. Oonasdivers also features several hotels at Na'ama Bay and the newly opened dive resort of Safaga as well as marine photography safaris and live-aboard dive boats. Marine biology tours on board fully equipped sailing yachts are bookable through Dive & Sail (0452 740919) from pounds 885 (not including flights) for one week.

(Photographs omitted)