It is an impressive descent into Ajaccio airport. Corsica is an island dominated by mountains. They fill its interior and sweep down to the waters edge. From the air it looks a wild island, with hardly a sign of human habitation. The ruggedness on the surface is reflected under the sea. Shotlines lead you down to enchanting underwater landscapes - to pinnacles of rock teetering over boulder-strewn slopes; sheer walls of gorgonians dropping down to 50m; and canyons and crevices weaving their way between the rocks, begging to be explored.

Off the southern shores of the Gulf of Ajaccio on the islands west coast there is much good diving to be had. In the middle of the Gulf, there is a small shipping beacon to which hardboats tie off. It is built on a slim tower of rock. This drops down 20m, where it breaks up into dustcart-sized rocks covered in brown and red algae, purple and rose-red fronds, sea pens and small red corals. The bottom here lies at 45m.

The viz in Corsica is superb. To British divers not used to being able to see much beyond their depth gauges, it might seem a strange feeling to begin a descent of the shotline and be able to see the divers on the bottom - 40m away - with brushstroke clarity. If youre not used to it, it can feel something like a first visit to the top board at the local swimming bath! When I pitched up in late September, the water was not at its peak temperature. But the new 5mm wetsuit I was wearing proved warm enough.

Corse Plongee, a CMAS school, operates out of Porticcio, 20km south of Ajaccio. Owner Nicolas Caprili estimates that there are at least 30 different sites to which he takes divers on a regular basis. These provide a variety of diving, from a leisurely mosey over a rocky bottom at 20m for the less-experienced, to some challenging diving for the more advanced. There is a depth limit of 40m for sport diving in Corsica, but this is not hard to bear - there is some marvellous stuff to see between 25-40m.

Corse Plongee has two boats: a hardboat which takes 40 divers; and a 7.5m RIB. The hardboat has a compressor on board, which makes it the perfect boat for a full day's diving if there are enough takers. Nicolas Caprili converted the boat himself when he came to Corsica 8 years ago.

As you might imagine, a dive boat converted by a diver has space where it is needed - for kitting up and de-kitting. When I was there, there were never more than 18 of us on the boat, and crowding certainly wasnt a problem.

We were an international bunch: French, Belgians, Italians, Americans and me - the lone rosbif, as the French would say! But, though our dive boat might have seemed like Babel at times, diving is an activity which is truly international.

Diving signals are either the same or translatable. OK is OK wherever youre from, and, of course, underwater experiences do not alter from national federation to national federation. For the information of British divers, Nicolas Caprili speaks very good English. He and his team made absolutely certain that briefings were understood before you strode off the boat.

Not being one for sprinting around under water, and as it had been a couple of months since I had last stuck my head under, I opted to take my early dives in the Gulf with a photographer.

Occasional Diver contributor Francis Le Guen was looking for a pair of divers to act as models on a rocky meander in the Gulf. My French buddy, Michele, was attractive and female, and I suspect that could have had something to do with his electing to use us as subjects! As debutants, Michele and I were, perhaps, not exemplary models. But I was surprised by how much effort and, above all, concentration is required to keep still centimetres away from an object for what seems an interminable time. As you might appreciate, trying to stay still for 3 or 4 minutes in the same spot on a wall which drops to 45m, absolutely packed with gorgonians, is no easy task. But, every time I thought Francis would have had enough, he motioned us to get still closer to the coral. Gorgonians are strange things. They remind me of the trees I used to make out of pipe cleaners at primary school. In locations where I have previously dived, you would have been fortunate even to stumble across a tiddler - let alone such forests of the things. On my fourth dive of the week, I rounded an outcrop at about 22m to be greeted by a view of a series of rocky pinnacles covered in gorgonians bathed in the rubescent sunlight of a late-autumn afternoon. The sight was so magical, it made me forget the cardinal rule of diving for an instant and I held my breath.

Off the south of the island, there is also some great diving to be had. Club Atoll dive out of Bonifacio -covering a wide range of sites along the south coast of Corsica, the northern coast of Sardinia (only 9km away), and the Lavezzi islands.

Lavezzi is a granite archipelago between Corsica and Sardinia. It is a marine reserve, and home to the renowned Merouville (Grouperville), which boasts the largest concentration of grouper in the Mediterranean. It was almost as if they had been arranged especially. With my buddy, Jean Attard, editor of the French sub-aqua magazine Apnea, I dropped down the shotline to a welcome party consisting of four of the brutes, all more than a metre in length. Before long, we were surrounded by very large and inquisitive fish.

Spearfishing has long been banned here and they were not in the least fearful. In all, we must have seen at least 20 during the course of our half-hour dive. According to Edmond Cridel, director of Club Atoll, this is quite a modest number.

Lavezzi has been a marine reserve since 1982, and the conservation effort is starting to pay off. In addition to the seemingly ubiquitous grouper, other marine life is also thriving. A substantial population of the increasingly rare peacock wrasse thrives here; and there is an abundance of red coral - which elsewhere in the Med is considered a rarity - at depths of only 25m. Morays, congers, scorpionfish, parrot fish, damsel fish, most of the 20 different species of wrasse found in the Med, cardinal fish, saupe, corb and langouste all make regular appearances on dives in the reserve.

Not surprisingly, considering the fertility of the waters, underwater photo contests are becoming increasingly popular in the Mediterranean, where they are seen as the conservationists alternative to the once-dominant spearfishing events. Club Atoll has taken advantage of the wealth of life around Lavezzi by hosting one in October each year. Britains Mark Webster achieved a second place in the 1995 contest.

Corsica takes its marine conservation seriously. The islanders are, quite understandably, aware that taking measures, both practical and legislative, to preserve their natural heritage is going to reap long-term economic benefits for the island.

There is next to no industry on the island, so none of the associated pollution. Neither has tourism yet taken off as much as in certain other destinations. All of which makes Corsica a delightful place to visit.

  • Corse Plonge, Teghi-Rotajolo, Route de Molini, 20166 Porticcio, Corsica (tel. 00 33 95 25 50 08; fax. 00 33 95 25 46 30).
  • Club Atoll, Cavalo Morto, BP3, 20169 Bonifacio, Corsica (tel. 00 33 95 73 02 83; fax. 00 33 95 73 17 72).
  • Corsican Underwater Federation, Quai de la Citadelle, 2000 Ajaccio, Corsica (tel. 00 33 95 25 12 58; fax. 00 33 95 25 08 18).