I’M SWEATING like never before. My sauna, cocooned in a blue and white wood cabin, with a smoking chimney and two outboard motors, is cruising out into the open sea near Gothenburg. Naked and glistening in 90-degree heat, I’m watching yachts and speedboats cruising around us.

I’m on Saunaline, which provides a trip of saunas, sailing and spa treatments among the islands of Sweden’s west coast archipelago. We drop anchor at a sheltered location and crank up the heat. Fifteen minutes of inspiring perspiring and I simply open the sauna door, step on to the deck and dive off for a refreshing shot of briny. We motor around, repeating the clash of temperatures several times over the next two hours.

On our trip the water was a balmy 19C (66F), but locals use Saunaline, also known as MS Värmeböljan, all year round, including winter, when she travels no farther than the ice-laden harbour. They also mix sweating with candlelit meals on deck, eating banquets prepared by a top chef.

We, however, returned to nautical normality. Next morning Telma, our 50ft eight-berth yacht, threaded her way out into the archipelago. Skipper Lars Fjelddahl has us diving around tightening sheets and unfurling sails.

Our target was Marstrand, Sweden’s equivalent of Cowes — home to the internationally renowned Swedish Match Sailing Cup. After mooring near a waterfront of seductive, multi-coloured wood mansions — “it has many bars and loads of sin”, Lars explained — we switched from sailing to kayaking. A glorious two-hour paddle took us past rocks coated with sun worshippers, along quiet inlets and through surging, choppy sea off Mar-strand’s exposed west flank.

Our good work was slightly undermined by bingeing on calorie-laden egg cheese, a speciality of the Bohuslän coast, followed by filet mignon at the Grand Hotel — dietary indulgence remedied only partially by a midnight uphill hike to a 17th-century Carlsten fortress.

Next morning brought more sailing. Food became healthier at the restaurant Salt and Sill on Klädesholmen, where herring were marinated in blackcurrant, lemon and ginger, and horseradish, each flavour supplied with bespoke schnapps.

This trip matches exercise with culture. We sailed into the harbour of Åstol, with its Nonconformist religious community, past Käringön, inhabited by fishermen since the 16th century, and through Kyrke- sund’s svelte rocky channel, a place of Viking legend.

Our final night’s anchorage, next to the tiny settlement on Lilla Kornö, meant another different workout. Lars swapped the yacht’s helm for training shoes and a cross-country run.

That just left a final morning’s adrenalin. A gale nudging force 8 chased us into Smö- gen for an alfresco feast of the island’s shrimps followed by pampering in the spa of the Smögens Havsbad hotel.

The dry peel and algae wrap was deeply relaxing. But it was the massage that bought me out in yet another cold sweat. “This is the real thing,” cooed Malin Larsson as she kneaded the muscles in my lower back, “a Swedish massage in Sweden from a Swedish girl”. My pulse went into orbit a final time and frankly that was quite enough excitement for one trip.

NEED TO KNOW

Getting there: Emagine (0870 9025399, www.emagine-travel.co.uk) has sailing packages from £850pp, including flights. Transfers, food and drinks, fuel and harbour fees are extra. Scandinavian Airlines (0870 60727727, www.flysas.com) has return fares to Gothenburg from £103.40.

Yacht charter: www.sjosportskolan.se.

Hotel: Smögens Havsbad (00 46 523 66 84 50, www.smogenshavsbad.se).

Further information: Gothenburg Tourism (www.goteborg.com); West Sweden Tourism (www.west-sweden.com); Swedish Tourist Board (www.visitsweden.com).

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