You can take the slow lane all the way down this river

The busy Canal du Midi isn't the only place to take a river cruise. Sarah Donnelly boards a solar-powered boat for a new tour of the Lot

Sun Seeker: Award-winning Le Kevin uses solar energy to gently power its way through the waters of the river (AFP )

There's a commotion on deck. A muffled voice booms over a speaker. Footsteps rumble down the corridor and then splooosh – the sound of a body hitting the water.

For the past 24 hours we have been creeping noiselessly down the Lot River in a solar-powered floating hotel, designed by our captain, Dominique Renouf. She launched her Lot cruise this summer, having decamped from the overcrowded Canal du Midi in search of peace. And she has certainly found it here – all morning, the beating of herons' wings and the occasional cry of some mournful water creature are all that have broken the silence.

I push aside the thin pane of glass between me and the action, and lean out of the window. Outside are the people with whom I will share my existence for the next three days. Philippe, the chef, casually rests on the handrail, smoking a cigar. Two British students, Emily and Raoul, watch their friend Adam battle the current. Dominique gazes from the hull at the object of this rescue – her blue-and-white striped parasol – awaiting retrieval.

Adam climbs back on board. The parasol is safe and calm is restored. We continue on to Casseneuil, where we moor up for the night. Heat has crept into every corner of the afternoon, and it seems the whole town has taken to the water. Canoes criss-cross the river; children look for frogs among the lily pads and teenagers launch themselves off a bridge.

In a hired pedalo, I make a noisy and ungainly entrance into a narrow tributary. I pass the stub of a ruin surrounded by neat lawns, pondering why they call this town Little Venice. My question is answered when I turn a corner to find a row of disintegrating timber-framed houses overhanging the river. They tower above me, and vines creep up their wooden pillars, like the river's green arms dragging them under. Their crumbling stucco fascias reveal red brickwork, and the lower-storey doorways are nothing but gaping black holes. I try to pass, but the low river becomes a reedy soup, and I have to turn back.

After dinner, Philippe and Dominique accompany me in search of a waterfall, which I am assured is impressive. Philippe takes the lead. He is lean and brisk and, apart from the slacks and trainers, bears a striking resemblance to Crocodile Dundee. He fosters a hearty cynicism towards the world and everything in it, including the English, given their role in the Hundred Years War. He leads us over fences, down brambly banks, over a bridge and to a dead end.

When we eventually find the spot, the sky is darkening. Dominique slaps a hand to her brow. Nothing but a dry, absurdly waterfall-shaped line of rock greets us. Green and grey streaks suggest the course of the flow, like the ghost of the vanished torrent. "Voilà, the waterfall!" says Philippe, lighting a cigar. We all laugh, and turn back.

The next day we stop briefly at Temple-sur-Lot. Claude Monet bought his famous water lilies here, and at the lily farm the rattle of frogs drowns out even the cicadas.

The river pushes us on, and at every village, weeping willows bow as we pass. The half-sunken wreck of a barge drifts by. It seems strange to think that only 35 miles away, the Dordogne cuts its cheerful path through campsites and ice-cream cafés. Here, life falls into a kind of slow motion but it is the languorous hours between destinations that truly mark out the days. The atmosphere is communal and homely. Dominique abhors the concept of luxury. "Here's the spa," she jokes, pointing to a puddle.

But the food is outstanding. As I'm a vegetarian with a cheese allergy, the phrase "meals included" usually terrifies, but Philippe leaps on the challenge. Eventually, he lets slip that he once worked in a top Parisian restaurant. At meals we all sit together.

The students, studying French at Warwick, are helping out on the boat in exchange for board. They are full of energy and engage warmly in conversation. When I become too tired to follow French, they rescue me. In the evenings, Dominique talks about the building of the boat. She was a psychiatric nurse, and when she conceived the idea of constructing a six-cabin, 30m barge powered by the sun, most thought her insane. The awards she has won have proved them wrong.

My final stop is Castelmoron, which on approach is hidden by the looming grey towers of a hydroelectric dam. Beyond the lock, a high-arched suspension bridge appears. When we stop, I run up it to get a better view of the town hall. I am reminded of the Thames at Richmond, and thoughts of home – emails and missed calls – shatter the peace. I try to shake them off, but it's no good.

The spell is broken. Beneath me, the boat's solar panels drink in the sunlight that will fuel our retreat back into the valley, while I must reluctantly turn again to the chaos of real life.

Compact Facts

How to get there

A week's cruise on Le Kevin with Naviratous (00 33 4 68 46 37 98; naviratous2.com) costs €700 per person, with children aged over six paying half price. Cruises operate from April until the end of September, departing Villeneuve-sur-Lot, a half-hour drive from Bergerac.