LE CROTOY, FRANCE — I stand barefoot in the soft sands of the Baie de Somme in northern France, feeling a little bewitched. Around me, my Canadian clan of five and a Parisian family of four are walking seven kilometres across the bay at low tide, an extraordinary stretch of sea and sky, salt marshes and mud flats. But it is our guide, naturalist Maxim Marzi, that I can’t take my eyes from as he floats through the landscape on utter emotion.
If there is magic in this bay — and I daresay there is — he is surely part of it.
“I love this place,” says Marzi, humming softly to himself, spreading his arms open wide, lost for a moment in the lure of the vast, ever-changing natural estuary, with areas of mud flats and salt marshes covering almost 70sq km.

Above: Naturalist guide Maxim Marzi sets out the journey and then playfully sinks in sand.

With a tidal range of 11 metres, it’s France’s second largest estuary of this type. Not truly land or sea, it blurs the lines — land when exposed at low tide, sea when covered by high tides.
“Crossing the bay is like an adventure,” says Marzi, a local guide, who’s been leading these popular three-hour excursions for a decade and whose great-grandmother was a fisherwoman here.
“You’ll cross a river, climb a micro-cliff, play with quicksand, slide on the mud banks and cross salt marshes and sheltered areas. The landscapes are changing according to the place where we are in the bay.
“And you know why? Because it’s modulated by the sea two times a day.”
It’s this twice daily tidal bore phenomenon that allows visitors to cross at low tide, clamouring down the sandy banks of Le Crotoy, a seaside fishing port with a rich pirate history, to arrive at Medieval St.-Valery-sur-Somme, a cliffside city with connections to William the Conqueror.
“We have to take very good care with the tide,” says Marzi, whose respect for the bay is always present. “The sea is going so far away that we don’t know if she’ll come back. But pay attention, she does, at the speed of a galloping horse. But when it’s low tide, the sea shore appears and it’s possible to walk on it for a few hours with a guide.”

Above: Guide Maxim plays with the family on the sinking sands.

Near St-Valery, Marzi points out quicksand and shows my daughters how to dance around and not sink. My husband wades in knee-deep to strike a Superman pose after Marzi shows him how. Always, he stresses safety. While the quicksand can be fun, it’s dangerous if you don’t know how to get out and the tide is rolling in.
As we walk through changing landscapes, Marzi points out life in the bay — workers foraging for samphire, glasswort or sea aster and the abundant wildlife. It’s one of the best areas for seeing common and grey seals and migratory birds.
The mixture of salt and fresh water in the river estuaries makes them rich areas for animals. Richest of all are the mud flats, filled with nutrients and home to invertebrates such as lugworm, ragworm and corophium shrimp. Wading birds, curlew, dunlin, plover, oystercatcher and sanderling feed on these invertebrates when the mud is exposed.
Wading into the mud flats is also a strange, yet fun sensation. “They call it the black foot,” says Marzi.
We’re here, walking with Marzi, on the tail end of a WWI pilgrimage through northern France. These last few days we reserved just for fun.
That’s how we find ourselves passing through a coded gate into the gardens of O Mylle Douceurs, a stone B&B in Le Crotoy that serves a sumptuous breakfast. We while away the evening wandering the waterfront, having dinner at Le Mascaret, a terrific brasserie.
Come morning, though, we’re frazzled, lost in our directions and worried we’ll miss the adventure — in the bay the tides wait for no one. I also fear I’ve made a mistake not packing water shoes in the precious space of our carry-on luggage. 
Worries disappear when we sink our bare feet into the sands.
This soul-nourishing landscape has long inspired artists, tourists, and dreamers. Painter Alfred Manessier famously wrote about the bay’s magical light and mirror effect. “I saw the Baie de Somme like a light, a mirror of the sky reflected by the wet sands. The eye is dazzled by this fusion between sky and sea.”
Marzi says the immensity of the landscapes and complexity of lights are something his guests love. That, and the wellbeing of the experience, the connection to nature and the exercise.

Above: The gardens of O Mylle Douceurs, a stone B&B in Le Crotoy.

“People say the place is authentic,” Marzi says, a perfect place to disconnect from everyday life, to share time with family and friends. And it’s not so far from Paris, Bruxelles, Lille or Reims.
Marzi says he loves how the bay never looks the same, depending on the day, and the tide. “Each tide is like a new painting.”
The crossing, he says, is a story of water and sediment. The bay is silting up, a natural process which affects all similar estuaries. The tide brings in sediments twice a day but is not strong enough to carry it all out to sea.
Cordgrass, one of the plants rapidly covering mud flats, traps sediments helping other salt marsh species to spread, so it’s full of sediments, nutrients generated by erosion.
“You know it’s like Feng Shui,” he says. “The wind and the water are elements which have built the landscape of the Baie de Somme.”