At its most intense, gorge-walking requires even more nerve than bungee-jumping. On a really hardcore gorge walk you follow the course of a young river, going where the water goes. This means that when you encounter a waterfall with a deep enough pool, you jump: some jumps can be up to 40 feet high. Although most of the dozen-odd outfits now offering gorge-walking also offer more moderate versions that are safe for nervous adults and children under 16, gorge-walking is always exhausting, drenching and at some point in the day, challenging to your courage - or lack of it. Surprisingly, no serious injuries have been reported from commercial gorge-walking outfits. But then it is a relatively new activity that has only been widely available for two years or so. Gorge-walking is potentially a very dangerous sport: all trips are led by qualified climbing and mountaineering instructors and the client to leader ratio should not exceed 6:1.

Whether or not you choose to leap off the waterfalls, you will have to climb up them, especially at the end of the day when you are climbing back out of the gorge, dreaming of toast, warmth, beer, sleep. But even then it is seldom over quite when you think. Gorge-walking routes often have have surprises at the end, perhaps making you shoot down a narrow rapid on your bum, or zip-wire across a narrow ravine faster than you ever thought you wanted to go, your legs dangling in the void.

Pembrokeshire, the Brecon Beacons and Snowdonia, all in Wales, are the main gorge-walking areas of Britain, although centres are beginning to spring up in Scotland. The most challenging gorge routes on offer at the moment are probably those run by Black Mountain Activities, based in Hay, who offer weekend trips into the Brecon Beacons. Meanwhile, down in Pembrokeshire, Preseli offer a strange variation on the theme: coasteering. You climb down a cliff, sometimes scrambling, sometimes abseiling to the sea below. Then, using a buoyancy aid, you bob across the water and climb the cliff out on the other side. Having to negotiate a watercourse, cliff, or even a stretch of sea necessitates a deep involvement with the terrain. You are constantly looking for handholds, footholds, ways to get from rock to rock, places to climb out of the water.

It's possible to combine a Preseli and Black Mountain trip over a long weekend. Trips can be tailored to nervous beginners or gung-ho madmen. Preseli's trips are residential and include all food, equipment and local transport, while Black Mountain will arrange local accommodation, but this is not included in the tariff. For this reason, you are best-off spending the first two days with Preseli, then driving or taking a bus over to Hay or Brecon for the gorge-walking. Both companies will pick you up from their closest towns if you arrive by bus.

FACT FILE

Contacts

Black Mountain Activities, PO Box 5, Hay-On-Wye, Hereford HR3 5YB, Tel (01497) 847897; Preseli Venture, Parcynole Fach, Mathry, Haverfordwest, Pembrokeshire SA62 5HN, Tel (01348) 837709, Fax (01348) 837656

Season

Coasteering: May to October; Gorge-walking: year round

Accommodation

Black Mountain will arrange local accommodation to suit your budget, whatever that may be (not included in general tariff). Preseli offers full board accommodation in a comfy converted barn.

Children

Only children over 12 years of age.

Insurance

Clients must provide their own travel insurance.

Safety

All guides trained in first aid, water and mountain rescue.

Tariffs

A full day's gorge-walking with Black Mountain costs pounds 35 per person, including a packed lunch but no accommodation. Preseli's Coasteering days are included as part of the centre's multi-activity packages (including mountain-biking and kayaking), though you can opt for Coasteering alone if you like. Two-day holiday: pounds 129.

Booking

Black Mountain: Advance booking is absolutely essential, as trips are increasingly popular. Also, full tariff must be paid with booking. Late bookings accepted if space allows.

Access

Black Mountain assembles clients at a central pick-up point, for transport onto the launching site, by minibus. Maps for how to reach the pick-up point will be sent on confirmation of booking. They can arrange a pick- up for those without cars. Preseli is off the B4331 near Mathry. Trains and buses run regularly to Fishguard or Haverfordwest. Pickups are arranged by the centre.