We walked across pebble beaches, rocky outcrops and pale sands, with the wind fierce in our hair: next stop Antarctica

About a year in advance I was invited to go on a walk, or rather an otter trail - in South Africa. A family reunion and some communal leg-stretching, fine, but why did they need an answer so far in advance? Once I arrived in South Africa, however, I realised that our walk was going to be more than a Boy Scout's nature trail. To say "I'm doing the Otter Trail" was like membership of an elite club. People were impressed and a little awed, as if you had remarked at dinner you were going to climb Kilimanjaro at dawn.

Roughly midway between Port Elizabeth and George, not far from the popular sands of Plettenburg Bay, the Otter Trail follows the coast from east to west in a narrow strip between the Tsitsikamma mountains and the sea. You cover 41 kilometres over five days, walking along a spectacular shore and winding under the great canopy of forest (with yellow-woods and stinkwood, white pear, climbing saffron, wild grape).

You cross pebbled beaches, pale sands and rocky outcrops; wade rivers; jump streams or step out high on the plateau above, with the wind in your hair. Next stop Antarctica. The surge of the waves is in your ears, rich air forces its way into long-forgotten corners of your lungs: all the elements conspire to bring on a state of near-perfect well-being and fitness.

You will be lucky to glimpse a Cape clawless otter (although these shy creatures give their name to the trail) and you almost certainly will not get eaten by a leopard, although they are in the forest along with a vast menagerie of other animals. Ornithologists can swivel their binoculars at more than 200 species of bird, and there are scores of fish and sea creatures from water snail to whale.

Where the cliffs drop too steeply to the sea, the trail zigzags up to the plateau and back down. This was to be more exercise than I normally take in a year but, just as the initial flush of enthusiasm turned to a blush of exertion, the perfect rock pool appeared. Jewelled dragonflies hovered in the still air as we swam and warmed on the smooth rocks and lazily dived in again across to a waterfall where you could stand, put your head back and drink cool fresh draughts. And then? An eagle sighted high up? Some strange fungus-like dinner plates thrown against a tree trunk? It was all a pleasant blur with my body happily walking on autopilot to the camp.

Two simple log cabins with six bunks limits any party to a maximum of 12. There is water and a fireplace for cooking. You eat anything with an immensely pleasurable hunger, sing any old rubbish around the fire and watch the embers glow away into the evening. Tsitsikamma comes from the Khoi word sietsiekamma meaning "place of clear water" and "water falling" and there are abundant streams, rivers and waterfalls coming down from the mountains - pure music to most drought-aching African ears. Indeed, that night the rain swept in, sudden and cooling. We slept with a steady drumming on the wooden roof and a gentle roar from the sea.

The second day was tough. The path climbed sharply through the forest and descended equally sharply. This was repeated ad exhaustam until we suddenly emerged with trembling knees on to a small sanded cove, with two huts, two small streams trickling down to the sea and a few seagulls. There was an atmosphere of primeval stillness. We slept that night as if drugged.

On day three we had the Elandsbos River to cross and several puff adders to negotiate. Slow and still if undisturbed, they can be quick if startled enough to attack, and are very poisonous. One was basking beneath some delicate white irises, confirming a suspicion that near beauty lies danger.

We came down to the camp right by the open sea in the bay of the Lettering River, with the waves disintegrating into spurting foam against some massive rocks. Two seals were playing in the rough eddies, careless of the immense swell. Further out, a school of dolphins was diving through the water as though on some vast trampoline just below the surface.

Pouring rain the next day soon reduced the path to a small stream, then increased it to a torrent. Crossing the Bloukrans River, the water was almost up to our waists - and this was at low tide. There are strong warnings against crossing if the tide is high or the river too swollen. We waded across, holding rucksacks above our heads and balancing each step.

The last night was spent in a sheltered bay, the huts set in thick overgrowth with a resident doe-eyed bushbuck calmly chewing the leaves and the sound of sietsiekamma all around. The sun returned for the final day, where a vigorous walk brought us to a magnificent view of Nature's Valley - simple name, splendid scenery.

A sheer climb down and a thigh-high wade across the Groot River, then we reached a wide expanse of white sands stretching out to the sea, with a small lagoon inland and a few holiday homes. Other people, houses, boats, cars, TV aerials ... being back in civilisation came as a shock.

Forget that health farm. Here we had been able to exercise in Eden.

Otter lottery: The Otter Trail is extremely popular and numbers of participants are carefully controlled. The National Parks Board runs a postal lottery system with priority being given to written applications received at least a year in advance. Write to: National Parks Board, PO Box 787, Pretoria 0001, South Africa (00 27 12 343 1991). Telephone links with South Africa are poor and connections to wrong numbers are frequent. From October this year until September 1996, the fee per person is about pounds 36.

Be prepared: You must be reasonably fit for this walk. Your backpack has to include food for five days, as well as cooking equipment, sleeping bag, clothes, medical kit, plus extras such as camera, binoculars and books.

How to get there: The nearest international airport is Cape Town, served direct from the UK by Air Namibia, British Airways and South African Airways. The lowest fare from London through Merchant Travel & Trade (01892 526747) is on Air Namibia for pounds 623.50, or on Air France via Paris for pounds 590 including tax; this is also available from Glasgow, Birmingham, Edinburgh and Manchester.

Otter alternatives: The International Otter Survival Fund (01471 822487) is organising a week-long otter survey on Skye and the island of Raasay in late September, price pounds 345 including food and accommodation.