His heavy brown hide was an intricate chain mesh, more like teeth than skin. Spectators gathered at the shoreline, where some wag played the music from Jaws. The audience was not helping. I wasn't sure how relaxed I felt about feeding sharks, either from the perspective of interfering with the natural world, or from the point of view of them being deadly predators intent on biting bits of me.

Nevertheless, there I was standing in my trunks chest-deep in a cove on the north coast of Jamaica with my arms wrapped around a four-year-old, 120kg male nurse shark. It was time to test 100 million years of ocean evolution. I held a dead fish a foot above his nose, then let go.

In a heartbeat, docile infant morphed into hungry hunter, lunging through my arms to feed. I jumped a foot. My hands felt every muscle on its belly tense and fire forward. The jaw-snap lingers in the memory.

Although big when fully grown, nurse sharks are pretty docile. However, they have a neat anatomical feature, a muscular cavity called a pharynx, which works like a vacuum to suck in anything that strays near its mouth. Hands need to be kept away from the business end, as one Jamaican handler discovered recently. I let my shark swim off with a thumping flick of his tail.

Pulling on a mask and fins I slipped back into the lagoon's turbid depths. Dorsal fins flopped through the surface everywhere. When diving in the Pacific, I'd been approached by reef sharks several times, but always in clear water. Here the underwater visibility was terrible – a storm had stirred up the sediment – and I could barely see my feet. Long dark shadows cruised right past my head and drifted a few metres beneath. After quarter of an hour I climbed out and gratefully counted my toes and fingers.

This aquatic afternoon was one episode in a high-intensity, four-day trip to test out the more extreme dimensions of this gorgeous-but-flawed Caribbean island. Most visitors to Jamaica (over-) indulge at all-inclusive resorts, but I was keen to get active.

For half a century, since the Fifties jet set of Fleming, Coward and Flynn, Jamaica occupied our imaginations as a laid-back tropical idyll (notwithstanding the drug-related violence of the capital, Kingston). Year after year, though, sprawling concrete resorts were thrown up on the north coast. That old glamour and charm can still be found in a select few locations, but this is an island trying to broaden its appeal, aware of the limits of buffet-to-beach hotel complexes so isolated from Jamaican life.

The curious visitor can explore the natural splendour of the mountain interior and the south coast, or take their pick from 500 years of colonial history. But the latest wheeze to reel in tourists sees the island rebrand itself as a centre for adventure sports.

At first glance, this is a highly implausible pitch. Visit Jamaica and you soon realise that the country's champion sprinters are doing the running for pretty much everyone. My own appetite for activity was only slightly blunted by the number of insurance waivers I had to sign (10). Nevertheless, I cheerfully signed to acknowledge the risk of mutilation and death for activities such as driving a dune buggy with the backdrop a verdant Jamaican mountainside.

As I set off, it seemed a bad moment to confess that I had failed my first and only driving test exactly one minute after pulling away from the test centre in Bedfordshire. My dune-buggy passenger and I were having too much fun. And anyway, we had helmets and were strapped into a steel roll-cage. So I dropped a leaden foot on the pedal and off we shot down the slope, taking a few branches with us. It resembled Maureen from the reality show Driving School meets Mad Max. We plunged into rivers, zipped haphazardly through forest tracks at 40mph and took corners sideways in a tailspin of rocks and choking dust.

At least I had some semblance of control, unlike when I tried racing dogsleds – a crackers Caribbean offshoot of the Alaskan tundra sport. Fifteen dogs, all rescued from Death Row at the local hound pound, dragged me on a sled through the muddy undergrowth. Then an activity that many travellers dream about – riding a horse along the beach. I found bouncing through deep waves on a snorting, bareback stallion, nostrils flaring as he fought the surf, strangely relaxing – and certainly less damaging to one's prospects of parenthood than the scariest adventure of all: zip-lining down from the peak of Mystic Mountain.

The ascent was agreeable: a slow chairlift to the top, cooking in the sun as sea kites hovered and I sucked in a stunning view. But before long, the cackle of laughter as we sped down through the tree canopy, whirring along wires from one swaying trunk to another, was broken by men's groans, as the ungenerous groin harnesses claimed another victim. The thrilling denouement, a 25ft vertical plunge, almost justified the distress.

It was only when we pulled over the spluttering dune buggies to stop for iced water, next to the vine-choked remains of the Blue Hall plantation in St James's parish, that I had a proper look at the greenery beneath my feet. My barrel of a guide, Ernie, showed me that the ground is carpeted in thorny Shame O'Lady herbs (mimosa pudica), which were sown around plantations in the 18th century. When trampled, the leaves of the plant collapse inwards – thereby revealing the route taken by escaping slaves.

Ernie also pointed out the prickle pine, or macka tree, which is covered every three inches with vicious thorns. Jamaican suitors used to be challenged by prospective father-in-laws to climb the tall trunk naked to demonstrate their devotion to the daughter.

That night, lazing with a rum cocktail in hand on the veranda of the Jamaica Inn, a small five-star property built on a private peninsula in the north near Oche Rios, I looked over to the next table to find Miss World 1993 (she didn't look old enough) teasing apart the juicy flakes of a grilled snapper. This was a pace of life surely more typical of the island.

Little has changed at the Jamaica Inn for 60 years. The colonial house is still painted Wedgwood blue and photographs of guests such as Marilyn Monroe and Arthur Miller decorate the saloon. The barman Teddy will serve you sandwiches and a lunchtime beer under a thatched umbrella on the beach, just as he did in 1958 when he started working there.

I emptied my glass while sitting outside one of Jamaica Inn's cliff-top cottages. The waves reverberated against the rocks below, and the night breeze blew the humid air off the island. Adventure sports were a wheeze, but when I return it will be with a driving licence, a hire car and two weeks to potter through the interior.

Travel essentials

Getting there

* The writer flew with Virgin Atlantic (0844 2092 770; virgin-atlantic.com), which flies twice weekly to Montego Bay and Kingston from Gatwick, with fares starting from £466. British Airways (0844 493 0787; ba.com) also flies to both airports twice weekly.

Staying there

* Jamaica Inn (001 876 974 2514; jamaicainn.com), Main Street, Ocho Rios, has doubles from $299 (£200), room only

* Half Moon (001 876 9532211; halfmoon.com), Rose Hall, has doubles from $250 (£160) room only


* Chukka Caribbean Adventures (001 876 953 6699; chukkacaribbean.com) offers various active tours of Jamaica, including horseback riding, river kayaking, 4x4 rides and dune buggy tours.

* Mystic Mountain Rainforest Adventures Jamaica (001 866 759 8726; rainforestadventure.com) offers rainforest tours, zip-line activities, plus a rainforest bobsled ride at Ocho Rios.

More information

* Jamaica Tourist Board: visitjamaica.com