THE look on my son's face said it all: two hours into his first canyoning trip, and he hadn't stopped grinning.

Sliding along natural flumes, zooming down a zip-wire, clambering through waterfalls, hurling over big drops, swimming through foaming rapids ... the descent of the Inchree Falls near Onich in Lochaber packs plenty of adventure into a short stretch of river.

Canyoning is like a cross between caving and mountaineering, using potholing techniques to descend mountain rivers and burns. It involves jumping, scrambling, swimming and sliding along the water course, and it is ideally suited to Scotland.

Although heavy downpours can leave gorges impassible, a damp day at any time of year is fine for a spot of river scrambling.

Vertical Descents, the firm in charge of our trip, has rigged the falls close to their Inchree base with a combination of steel cables and rope lines to help clients stay safe. This isn't, however, some sanitised adventure. It retains something of the nature of caving and climbing; you need a bit of self-reliance and it's hard physical work.

And, as I was to learn for myself the next day, the guides aren't there just to show the way and go through the safety motions.

The Inchree trip builds up from easy jumps – maybe from 10 feet up into deep water – traversing pools, and scrambling the banks. There's the zip-wire, a wonderful climb up into the space behind a vast foaming waterfall curtain, and one superb white-knuckle moment, the big leap.

To get to it we scramble up a vegetated bank to come out at a breath-stopping drop, 35ft above a dark pool with a waterfall to our right. I watch from behind as my teenage sons Rob and Joe disappear over the cliff edge.

Our guide is with us, and below his assistant waits to direct jumpers to a safe haven on the bank.

It seems enormous: as a climber I spend a lot of time avoiding falls like this, and now I'm going to throw myself off deliberately. I launch myself before I can start thinking. It's the nearest a man can get to flying unaided, and I count a couple of full beats in the air.

Arms aloft, feet pointed down, I hit the water and shoot maybe two metres below the surface before bobbing up again, adrenalin surging through my body along with a feeling of relief.

Back at the centre we strip off the heavy wetsuits – your body is encased in 16cms of neoprene and insulation, plus a buoyancy aid like body armour and a waist harness with a strange plastic nappy hanging from it to save wear on the wetsuit seat and help your backside stick to the rocks. Helmets are worn at all times.

We're staying at the Corran Bunkhouse, next to the Corran Ferry near Inchree, and an ideal base for a canyoning weekend with a well-equipped kitchen and an efficient drying room. We wolf down three big plates of steak and chips at the The Four Seasons at Inchree and wonder what tomorrow will bring.

The next day dawns bright, with ragged clouds, blue sky and a blustery wind, and the trip to nearby Allt Nathrach, at Kinlochleven, is on.

Less than an hour later I am floating through a lost world, with slender branches hanging down, huge, sculpted, water-fluted cliffs, ferns, vast hanging carpets of moss, gargoyle-like roots and bubbling water.

The Allt Nathrach is far more of a gorge than Inchree, and the only way to see these wonders is by canyoning.

Our guides have the skills to get into canyons where few people have ever been, and even this water course, which they travel regularly, feels wild, raw and remote.

Unlike Inchree it is hard to escape. Features such as slides and jumps are more spread out, with sections of pure floating and swimming in between. There are no cables here, just a couple of fixed ropes on a crucial section.

After a couple of hours we come to the big jump. A 45ft water fall is to our left and we have to jump that distance down into the circular cauldron of black water it plunges into.

The boys hurl themselves down and I take a quick glance and throw myself into space.

To get down the next waterfall we must be lowered on the rope. At the bottom I am pounded by the water, and swim to the next stance coughing and spluttering. I'm fine but Rob is feeling a bit battered. I stick close behind him for a while but he's soon back in the swim, swirling down the waterway to the final slide down a short, powerful fall.

Assuming it'll be easy, I slide down and hit the water.

I bob back up, bump into overhanging rock, am swirled back down. I shoot up but the waterfall is pounding on my head and I go under again, coming up gasping. It feels desperate, and I am out of control as I am whirled around. My swimming strokes are useless, and I am genuinely scared.

Then the guide is in the water next to me, shouting and shoving me firmly across the pool. Not much further along we climb out of the gorge, back into normality.

My boys are delighted with the trip. I'm a little more sober, but reflect that this was a real adventure, only made possible by the guides and their training and knowledge.

I am, though, wondering about buying a canyoning wet-suit ...

Vertical Descents

Inchree, Onich, Fort William, 01855 821593

www.verticaldescents.com

Inchree Falls trip: £50 per person

Allt Nathrach: £85.95 per person

Corran Bunkhouse

South Corran, Onich, Fort William

01855 821 000

£18 a night per person

www.corranbunkhouse.co.uk