I think the South African Tourist Board is missing a trick when it comes to advertising Cape Town. Forget glossy pics of vineyards and beaches, it's damn cheap. With the rand hovering around 12-13 to the pound, South Africa is still a bargain. This is a boon for those who want an active holiday. Over the past few years, Cape Town has established itself as an adrenaline junkie's paradise but it's not just the cost that attracts visitors. The fact that the activities are relatively concentrated means you can mountain bike in the morning, scuba dive in the afternoon and kayak through seal colonies as the sun goes down.

White shark cage diving

'We've only had two days in the last six months when we haven't seen a shark,' said our guide Mike Ladley, originally from Blackpool, after we - a couple of Brits and six Swedes - sat on our boat near Gansbaai, 102 miles from Cape Town, for five sharkless hours. A reassuringly thick cage was poised, ready to be swung over the side. It never happened.

To be fair, I was there in February and peak spotting season is April to August. 'The water's too cold now,' said Mike. None the less he reckoned we'd have a 75 per cent chance of being 'investigated' (translation: chomped) if we had to swim the 500 yards to shore.

Mike is in love with sharks - a few years ago he actually kissed a great white. He also insists there's nothing wrong with cage diving (those against say it encourages sharks to associate humans with food). 'Great whites are not deep-ocean creatures. They stick fairly close to the shore, so we're not bringing them in - they're here already. More people are swimming in the ocean, so more are going to get attacked,' he said. No one looked like turning into a human Scooby-snack today.

And then, all hell broke loose around the nearest boat, 40 feet away. Even though not right next to us, there was still a collective cry of skit ocksa ! ('Oh shit', in Swedish) as a huge fin parted the water. A four-metre grey shadow was visible under the surface, which even at that distance was enough to make the hairs on the back of my neck stand on end. The shark stayed around for 10 minutes then vanished.

White Shark Projects (00 27 21 552 9794) has day trips for 1,100 rand (£85) per person, R100 less if you drive yourself to Gansbaai. As the cage floats just underneath the surface you don't need to be a qualified diver.

Mountain biking

When a mountain biking trip was suggested through local vineyards, I blocked out 'mountain' and concentrated on 'vineyards'. However, when our guide turned up in fluorescent Lycra, looking like he was about to tackle the Alpine stages of the Tour de France, I don't think getting sloshed was top of his agenda. Luckily for me, the four other punters on the half-day trip to Constantia, round the back of Table Mountain, were on my wavelength. After trails through a shady wood and along pretty country lanes we were on the receiving end of a rather cheeky Merlot, well before lunch.

The problem wasn't the gradients, or cycling under the influence, but the heat, as temperatures hit the high 30s. Serious mountain bikers would probably think the day very tame and, for the really keen, trips down near-vertical tracks can be arranged.

For those in the 'mildly unfit' category (i.e. me) the combination of a few challenging sectors, lovely scenery and the chance to be a pretentious wine taster (I'm getting Tarmac, I'm getting Granny's vest) all add up to a fun day.

Downhill Adventures (00 27 21 422 0388) charges £27 for the trip, which includes a picnic lunch. Other trips available include to Cape Point (also £27 ) or a descent from Table Mountain for £19.

Abseiling

As someone who is not a big fan of heights, I thought I was remarkably calm as I stepped backwards off the top of Table Mountain, which claims to have the world's highest commercial abseil operation. All was going well as I pushed away from the rock, one foot precariously following another, repeating the mantra 'look out, not down, look out, not down'.

About halfway, you pass a massive overhang. All of a sudden you're dangling in mid air. I involuntarily twisted round, catching a glimpse of the beaches of Camps Bay and Clifton way, way below me, and I started whimpering like a sick puppy. Once that little shock was over I inched down as quickly as I could until, about 10 minutes later, I was back on terra firma, shaken and stirred.

Abseiling can be arranged through Adventure Village (00 27 21 424 1580). Price is £20, plus the cost of the cable car to and from the top of Table Mountain, £7 return.

Sandboarding

Never having sandboarded before, I'd expected some technical explanation before launching myself down the dunes at Betty's Bay, 90 minutes east of Cape Town. Instead, our instructor told us to wax our boards, point ourselves down the beginner's slope and go for it. I launched myself down the 60ft run, quickly picking up speed and staying upright (just) before coming to a very wobbly halt. If this was an Olympic sport, I don't think the Russians would have given me a six.

After we'd mastered the baby slope the more adventurous climbed to the top of the 1,000ft hill. Landing on sand, even at speed, seems gentler than on snow. The sport is easy and good fun. The downside? Climbing up dunes when it's 35C and sand gets everywhere.

Downhill Adventures (see above) organises a day's outing to Betty's Bay, including transport, instruction, lunch and a chance for a swim in the sea at Gordon's Bay on the way home, for £35.

Kloofing

Canyoning - or kloofing as it's called in South Africa - is like hiking, with one difference: when the path runs out you go to the top of the nearest rock and jump off into the deep, natural pools below.

Our small group walked five miles along the picturesque Steenbras River Trail, about an hour out of the city, and then came to our first challenge, a 23ft jump, which I just about coped with. On a stiflingly hot day the drop into the icy water was welcome. My vertigo kicked in at 32ft and I sat in the sun to watch everyone else take the plunge. However, I did manage the 46ft jump that followed because the way the shadows played on the water meant it didn't seem that high. It was.

Adventure Village (see above) organises a full day's kloofing at the Steenbras River Trail, including lunch and an abseil down a waterfall at Kamikaze Canyon, for £35.

Other activities

Learn-to-surf day trips can be organised through Downhill Adventures (see above) for £35.

The same company also has a seven-day Cape Great Eight Adventure Experience that departs every second Monday. Comprising shark cage diving, tandem sky diving, sandboarding, mountain biking, abseiling, sea kayaking, surfing and quad biking, this costs from £650 per person (two sharing), which includes 'backpacker-type' accommodation, lunches and activities.

Factfile

Getting there: South African Airways flies daily to Cape Town from Heathrow from £594.60 return (0870 747 1111).

Cape Town is packed with excellent value B&Bs. Britford House, for example, in Sea Point (00 27 21 439 0257, email: popkissm@iafrica.com) charges from about £40 for a double room.

South African Tourist Board: 0870 155 0044. Also see www.cape-town.org and www.capetourism.org.

Car rental: Holiday Autos (0870 400 0011) has cars from £91 per week.