The sun eats its way through the mid-morning mist above the river and its rays begin to beat down on us. It is going to be a beautiful day on one of the largest and most beautiful stretches of river in Ireland, but our boat is alone.

"If this was the Norfolk broads, your head would be turned with boats already," says our guide, Billy Montgomery. He has a point, with the school holidays underway, boating enthusiasts are swamping rivers all over Britain.

Across the Border, the Shannon will also be doing a roaring trade, but during the six hours spent on the Upper Bann I see not one other boat on the river. The phrase "Hidden Ulster" could have been coined for this river.

Although based in Co Antrim, Billy's company, Irish Voyageurs offers river expeditions to both tourists and experienced canoeists throughout Ireland. It has two large Canadian war canoes, each capable of carrying up to 12 people - fewer if they have camping equipment.

The novelty is that those on overnight expeditions sleep not in a conventional tent but in a large, green, Norwegian teepees. They may look out of place in Ireland, but each is spacious enough to sleep eight people comfortably, and they are well suited to the weather. Dismantling the tent, Phil McKee, Billy's partner points to metal pegs hanging from its central pole. "These are meant to be for drying your reindeer pelts, but we use them for drying coats," he says.

This weekend Billy and Phil are playing host to four guests from the Republic, on their third trip. Conor Palmer from Co Kildare, his cousin Kevin Durrad and his brother-in-law Paul Beddy are joined by Paul's 16-year-old son, Neil. Purely in the interests of research, they are joined on the water by a reporter who is convinced the canoe will capsize the moment it is set free from its mooring. It does not, and soon the canoe is gliding upstream on impossibly smooth water that calms even the most nervous oarsman.

The Upper Bann, which drains Lough Neagh to the sea, was dredged and cleared in the early 1930s. The spoils from the operation were left on the banks, with trees planted to anchor them. Seventy years later, mature ash, sycamore, oak and birch line the bulk of the shore and the effect of the wall of greenery is Amazonian. Although it is only three or four trees deep, the barrier isolates you to such an extent you could as easily be in Canada.

On this trip, first heading south of Kilrea, then, north of it, the priority is fishing, not distance. But as some play their lines out in the boat's wake, others have to keep paddling. There is a real satisfaction in propelling a boat along, a feeling made even greater each time we stop. At every stop, the birdwatchers on the boat have much more luck than the fishermen. Sedge warblers and swallows abound, but when Paul and Neil are asked what is for lunch, someone answers for them. "Not fish, anyway."

After only a couple of hours we are back for lunch, but Billy says not every trip is as relaxed as this. "We had a group of rugby players out for what I thought was a booze cruise, but when they rowed, they rowed. We went from Toome to the sea (almost 40 miles) in two days." Phil has had the canoes out around Rathlin Island in a gale.

In true camping fashion, guests are expected to muck in at the site. "One of the things about these holidays is that the guides don't do everything, the plebs help out," Billy says.

After lunch, the site is cleared and packed up. The tent shrinks to no size, a plus when everything might need to be put into a canoe for one of those only-accessible-by-boat campsites.

Phil skippers the afternoon leg. Other stretches of the Bann are more in use - there is a marina in Ballymoney offering waterskiing, for example - but for the moment the river remains woefully, or wonderfully underused. "You can get so used to not seeing any other boats that you begin to think of it as your river, and get cross when you do," says Phil.

At Movanagher, a small cluster of houses was the site for a major excavation. "This was to have been the third town settled by the London Company along with Londonderry and Coleraine. Except O'Neill kept attacking and they couldn't hold it," says Phil. " Probably just as well, or this would all have been Marks & Spencer and Dunnes Stores," he says, gesturing at the empty fields and leafy banks.

After a sunny, sultry day on the water you'd sign up for another, but what about when there's more H

At present, the underuse of the Bann means Irish Voyageurs is a part-time concern, but with greater peace and investment this could change. There are plans to reopen the Ulster Canal, linking Lough Neagh and the Bann to the Erne and the Shannon, and extending it as far away as Dublin and Waterford. "Canals have turned a corner. They are no longer seen as a bygone relic - they have a real future as a tourist attraction," says Phil.

Contact number for Irish Voyageurs from the South: 048-25631730 and from within the North 028-25631730