An expedition on the fastest Norfolk “mussel flat” boat ever built by fishermen of yore does not, I have to admit, sound particularly restful. But a meditative journey is what’s promised, and the sight of Saffron’s clean wooden lines and simple interior is immediately soothing.

This boat was once propelled along the creeks by one fisherman and a single oar, laden with two tonnes of mussels when returning home. Now she’s been lovingly restored for our skipper, Zoe Dunford, to lug stressed-out tourists for a “wellness sail”.

It’s a zero-carbon trip, with no motors or machines, and one restricted to four paying travellers not because of Covid but the size of the boat. Usually, I’d take photos and discreetly check my inbox but Henry Chamberlain, who set up the Coastal Exploration Company by restoring beautiful old boats to make eco-friendly excursions, orders us to turn off our phones and packs them into his dry-bag.

Zoe begins by manoeuvring away from the harbour at Wells-next-the-Sea using that single oar mounted on the rear of the boat, twisting it in a circular motion. It looks like hard work, and we’re forced to avoid a few small motor boats zipping around – although we can’t avoid their passing judgments.

“It’d be a lot quicker with the sail,” shouts one fellow seafarer. It wouldn’t, Zoe says calmly, because although Saffron has a sail there isn’t the space in this section of the tidal channel to tack into the breeze.

“Put your back into it!” cackles a dog-walker on the sea bank. “Look at the blokes there not having to paddle!”

“Can I do anything?” I ask Zoe and Henry, embarrassed.

“Your job is to relax and be well,” says Henry firmly, before explaining the journey ahead. “It’s the nature, the peacefulness but also the tidal rhythms, driven by the heavenly bodies, the sun and the moon.”

For the 40-minute outward voyage Henry asks us to close our eyes and slow our breathing, think about that tidal pull and its slow force, and just quietly notice the sounds of the marsh. The incoming tide is carrying Saffron into the marsh while also pulling us to find the peace within ourselves.

For an ex-Marine, Henry’s good at this meditative stuff. I close my eyes. At first I’m assailed by visions of emails requiring replies and tasks I’ve neglected. Then I’m overcome by yawning. Then, suddenly, I’m aware that all I can hear is the gentle slop and sloosh of water against prow as Saffron rocks gently with Zoe’s oar-work. Actually, no – there’s the shrill fuss of a redshank and the delightful burble of a curlew. And in the distance, the low conversational chatter of geese swelling up from the marsh. I take a peek: the birds rise like a plume of smoke on the horizon and slowly drift across the blue sky.

I didn’t know the migratory pink-footed geese were back but their presence, often in flocks of thousands, is one of the great gifts of autumn and winter on this coast.

We pull into a small creek where Zoe sticks her oar into the mud for an anchor. We’re now reaching the top of the tide, says Henry, and things are in balance. We climb out onto the bank and the mud feels cool and delicious under our toes. Henry encourages us to have a swim in the creek to wash away the last of our stresses. After a careful inspection, we take a running jump off the bank into the creek, which is unexpectedly deep. Yellowy-brown at the surface, it’s also unexpectedly clear once I’m under water and the cold shock isn’t too extreme – sun-heated water trickles from side creeks, creating pleasantly warm patches. As the recent wave of books and articles about the joys of wild swimming remind us, there can’t be a more effective or instant cure for melancholy or anxiety than a cold sea swim.

The creeks are intimate and secretive, and wild creatures lose their fear when humans behave like seals. A small bird hurtles towards my head, low over the water. It’s not a wading bird I know. Hang on! It’s a kingfisher! On the salt marshes! I always assumed they were a riverine bird, not a seaside one.

Back on the boat, Henry prepares tea: samosas, quiche, tomatoes, Norfolk dapple cheese, samphire freshly picked from the marsh, chocolate brownies and a hot drink. We talk in the soft autumn light about old smuggling days, the nearby ruins of a “prevention hut” (where local officials kept a lookout to try to stop smuggling on the creeks), and the new users of the marsh. The north Norfolk salt marsh – inaccessible, sometimes dangerous, and unprepossessing at first glance – may be the last wilderness in southern Britain but more people than ever before are exploring this once-unpopulated landscape. Almost everyone, however, is kayaking – often with a dog in a life-jacket balanced on the front – and appreciating and not detracting from the peace.

The tide has turned, and we turn too, using its movement – and the sail, this time – to bear us back towards Wells. Henry asks us to consider the cycle of energy, how the tide propelling us encourages us to release our anxieties and leave our troubles (but nothing else) on the marsh. He suggests we slowly turn our newly calmed minds outwards again, look to the future and consider how we might create more peace for ourselves and others. “We get an enormous amount from nature,” he says. “We should try and put something back.”

The lowering sun on the water lights a path back to Wells. Saffron’s ochre-coloured sail billows and we are gently carried back to the harbour, where boats glint in the last light of day. The great expanse of sky, marsh and sea is a truly calm space, and this skilfully executed expedition has had the desired effect on my brainspace.

• Half-day wellness sail for four, including food, £85pp, coastalexplorationcompany.co.uk