We started in Killaloe, Co Clare, which is the southern end of the Shannon navigation, at least for hire boats. This was the trip. All the way to Co Fermanagh to see the mouth of the Ulster Canal.

We promised each other long summer evenings watching the sun descend across Lough Derg, slow journeys meandering through the flat midlands countryside and the sight of the mist as it rises off Lough Bofin on a summer's morning.

We spoke of eating outdoors, on the deck of the boat or in the waterside restaurants and pubs, of the banter with neighbouring boaters and of the slow, slow pace of it all.

And that is exactly the way it happened.

Two hours into the journey the evening was so nice we decided to spend the night at Garrykennedy on Lough Derg in Co Tipperary. Garrykennedy consists of little other than two pubs and a harbour and many pleasant evenings have been spent in both pubs. It's popular with families, because the pubs serve food and children's meals, and you can almost hear the collective sigh when the last one goes to sleep on the boats and the deck chairs come out.

Next morning, after a choppy journey, we arrived at the swing bridge in Portumna, with enough time to cook lunch or visit Portumna Castle before the bridge opened. Left alone for a few hours, I made a classic blunder. I went back out on the lake in the boat with no other craft in sight. It had become very rough and suddenly the anchor was flipped overboard and became stuck in the lake bed. Bobbing there, I blessed mobile phones and explained my predicament to the Emerald Star base in Portumna. They despatched one of their boats and between us we drove our boat across the anchor and hauled it in.

Chastened and in the calmer river section north of Lough Derg, we got through Victoria Lock without any problems, and in Banagher we prepared a meal and ate on deck. The weather was blustery, but we got chatting to other boaters; it was pleasant to sit in the fresh air and relax with a cool draught. We vowed to take Lough Ree with extreme care.

The following days slipped by slowly as the river meandered wide and slow-flowing, the boat going at no more than a fast walking pace. We passed the entrance to the Grand Canal, which leads to Dublin, and the Ballinasloe Canal, which was closed in 1961. We wandered about the monastic ruins at Clonmacnoise and then went on to Athlone, where we spent the night at the marina.

The next day we crossed Lough Ree in a convoy of boats to Lanesborough. An ESB power station is here and many miles of narrow-gauge railway bring small trains feeding the plant with peat. We passed the entrance to Richmond Harbour, where the Royal Canal enters the Shannon, and continued on under the raised bridges at Tarmonbarry and Rooskey.

We ate well in the local pub that night, but were under way early the next morning and crossed loughs Bofin and Boderg as a gentle haze rose off the water, holding the promise of really fine weather.

Here we were in the upper Shannon, my favourite part of the navigation. The sun sparkled on the water and we were tempted up the Boyle River, where the trees overhang the water. There was time for lunch at Clarandon Lock before entering Lough Key. By now, we had lost all sense of time, and it did not seem to matter that we had turned off the route to the Shannon-Erne link. At some stage we went back, because I remember the daunting series of locks leading up to Lough Scur on the Shannon-Erne link. They are all automated and the smart cards which open them also operate showers, lavatory and laundry facilities along the way.

After Ballyconnell, we were on the Woodford River, with Fermanagh on the left and Cavan on the right. There was a turn for Belturbet on the Erne River, but we headed for the calm Quivvey Waters and the mouth of the Rinn River. At Wattle Bridge we came upon the holy grail: this is where the Ulster Canal began. With the second feasibility study under way, most boaters believe it will reopen.

Some day, when that happens, and we have a month to spare, we will be back.