The first thing you learn about the Nantes-Brest canal is that it does not actually run from Nantes to Brest any more. The dam that created the Guerledan reservoir in the 1920s drowned a long stretch near the middle, and the summit feeder broke down decades ago, so what was once a 385 km waterway with around 238 locks is today a string of navigable sections rather than one through route. I spent a fortnight on it last spring in a hired cruiser, and that fragmentation turned out to be the making of the trip rather than a disappointment.
Here is how I would shape two weeks on it, and what nobody tells you before you book.
Pick your section first, then your boat
You cannot cruise the whole canal, so the honest planning question is which part. The cleanest two-week trip uses the eastern, river-fed run from the Loire-Atlantique end up through Redon and on towards Pontivy, where the canal borrows the Vilaine and then the Blavet. This is the stretch where the hire bases sit and where the locks are reliably open through the season.
The Blavet section alone runs about 57 km with 28 locks down towards Lorient, and the canalised Vilaine and Oust above Redon give you the gentle, lock-by-lock cruising people picture when they imagine French inland boating. If you want the full mechanics of how these chambers work before you arrive, the piece on how a French lock works is worth ten minutes.
Hire boats here are mostly Freycinet-friendly with shallow draught, which matters because the Breton canals silt and run thin after a dry summer. Confirm your boat's air draught too. The fixed bridges in Brittany are lower than on the big eastern canals, and the air draught on French canals catches out crews who assume a metre of clearance is plenty.
Week one: Redon up the Oust
Redon is my favourite place to start. It sits at the crossroads of the canal, the Vilaine and the river Oust, with a basin in the town centre and shops two minutes from the pontoon. We provisioned hard here because the country north of it empties out fast.
A realistic first week, taking it slowly:
- Redon to Malestroit, two or three days. The Oust valley is broad and quiet, with herons on every reach and lock cottages that still have keepers in summer.
- Malestroit itself deserves a full day. It is a tiny medieval town built around the water, carved stone faces leering off the old houses, and you can tie up in the middle of it.
- Malestroit to Josselin, two days. This is the postcard leg. You round a bend and the four round towers of the Rohan chateau rise straight out of the canal, and there is a mooring directly below them.
We averaged the usual canal crawl, somewhere around 6 to 8 km/h between locks, and stopped for lunch whenever a lock-keeper did, because in France everything pauses between roughly midday and one o'clock and there is no fighting it.
Week two: Josselin towards Pontivy
North of Josselin the locks come thicker and the country gets wilder. The flight up towards Rohan and on to Pontivy is where you earn your evening glass of muscadet, and where having a second crew member on the lock side genuinely speeds the day.
Pontivy is the practical top of this navigation for most hire boats. Beyond it the old summit pound towards Carhaix is not navigable, having been cut off when the 63 km Hilvern feeder failed, so Pontivy is where you turn the boat and start back down. That is not a hardship. Pontivy is a real working town with a Napoleonic grid laid over a medieval core, and the run back down the Blavet locks feels different from the climb because you finally relax into the rhythm.
If you have the legs for it, the lower Blavet towards Hennebont and the sea is a beautiful descent, but most one-way and return hires turn at Pontivy to keep the days sane.
The lock-keeper clock
The single biggest planning factor on this canal is not distance, it is the keepers' hours. Locks open around nine in the morning, shut for that sacred lunch hour, and close in the early evening, with the exact times varying by section and by month. Lose an hour dithering over breakfast and you can lose a whole flight of locks for the day.
I kept a paper note of the day's first and last lock times taped above the chart table. It sounds fussy. It saved us twice. The wider canal etiquette and what a typical day actually feels like is something I went into in daily life on the French canals, and the Nantes-Brest is exactly the canal I had in mind writing it.
Paperwork and money
Two practical things to sort before you cast off.
If you bring your own boat rather than hire, you need a VNF licence, the vignette, priced by boat length and trip duration, and the 2025 rates rose slightly with a green discount for cleaner engines. Hire crews can ignore this, because the fee is baked into the rental, but owners should buy online before arriving rather than guess at the first lock.
You also need a recognised inland certificate. France accepts the ICC with the CEVNI endorsement for foreign boaters on the canals, and I would not rely on a coastal certificate alone. The detail on which papers actually count is in the CEVNI and ICC licence for French waterways, and it is the kind of thing worth getting right at home rather than arguing about at a lock.
The towns that earn a night
People rush the Breton canals because the locks are tiring and the distances feel short on the map. Resist it. The towns are where the trip lives, and several deserve a full day rather than a quick tie-up.
Redon repays a morning even if you start there. The old salt and slate trade built handsome quays, and the town sits at a genuine crossroads of waterways, so there is constant comings and goings to watch from the basin. We used it as our reprovisioning anchor at both ends of the trip.
Malestroit is the one I would go back for. It is barely more than a village, but it grew rich on the river trade and spent the money on stone, so you tie up among carved house fronts and a church porch crawling with medieval sculpture. We ate galettes within fifty metres of the boat and watched the light go off the water.
Josselin is the show-stopper, and not only for the chateau. The lower town, the Sainte-Croix quarter by the river, is a tangle of timber-framed houses that has barely changed in centuries. We climbed up to the basilica, looked back down on our own boat tied beneath the towers, and felt thoroughly pleased with ourselves.
Pontivy splits in two: the medieval tangle around the old castle, and the rigid Napoleonic new town laid out when the place was briefly renamed Napoleonville. Walking from one to the other in ten minutes is a quick lesson in French history, and there are proper shops for the run back down.
Bikes, bread and the towpath
The single best decision we made was to load two bikes. The towpath alongside the Breton canals is part of a long-distance cycle route and is mostly smooth, level and traffic-free, which changes how you run the day. One of us would ride ahead to the next lock to help the keeper or scout a mooring, and every morning someone pedalled into the nearest village for bread before the boulangerie sold out.
It also rescues the rest days. On a layover you can ride ten or fifteen kilometres into the countryside, see a chateau or a chapel, and be back for lunch. With locks to work and a boat that crawls along at walking pace, the bike is not a luxury on this canal, it is core kit.
What two weeks really buys you
The honest answer is roughly Redon to Pontivy and back, with proper days off in Malestroit, Josselin and Pontivy, at a pace that lets you cycle the towpath to a boulangerie each morning. We covered well under 200 km in fourteen days and never once felt we were dawdling.
If the canal disappoints anyone, it is the crew who booked expecting to cross Brittany coast to coast and discovered the middle is a lake you cannot transit. Go in knowing the navigation is in pieces, choose the eastern river-fed run, and the Nantes-Brest gives you the quietest, greenest, most genuinely Breton fortnight on the whole French network. Bring bikes, learn your bonjour, and let the keepers set the pace.
