With fronds like these

Madonna, I can confidently promise, has never graced this spa. Jade, Tara, Kate - you name the pampered poppet, she won't have been here.

Although the experience on offer is &uoml;ber-organic and unique, at Kilcullen's Seaweed Baths, on Ireland's Mayo/Sligo border, bathers are more likely to be bone-weary farmers recovering from a hard season's toil than a therapy addict notching up a new treatment on her Gucci belt.

An Irish friend, hearing that I planned to visit the wild west coast, insisted I should seek out "the ultimate bathing experience". From Knock Airport it was a 40-mile drive across bungalowspeckled farmland and fast-flowing salmon rivers to the Atlantic coast, and the raggle-taggle, pastel-painted seaside village of Enniscrone. A left turn after the sculpture of a giant pig and before the grocer-cum-bar brought me to Killala Bay: five miles of sandy, lonely loveliness, with enough shades of blue in sea and sky to inspire a Fired Earth Celtic range.

And facing it were the Seaweed Baths - a black-and-white, single-storey building with dinky stone turrets and a curve of windows that encompassed the whole view.

Opened in 1912, the year this same ocean sucked the Titanic into its depths, the then fashionable bathhouse claimed to offer relief from rheumatism as well as a restorative experience for those brave enough to wallow in heated seawater pumped via a rubber hose from the bay, with a bucketful of freshly gathered fucus serratus, thrown in.

"That's Latin for brown, bubbly seaweed," explained Christine Kilcullen, whose husband Edward is the grandson of the original owner. Most mornings, fiftysomething Christine, accompanied by her labrador Trampus, descends to the beach in her wellies to replenish her stocks.

As she dispatched a helper along the mandarin-coloured corridor lined with bathing rooms to prepare my "treatment", feelings of uncertainty crept in.

In the boiler room, where plastic sacks of seaweed are briefly steamed to release the oil and iodine that give it its moisturising, detoxifying properties, I'd spied a pile of rust-coloured crabs that had sidled past the filtering process. And though the bathroom - gargantuan porcelain bath and peacock-coloured Deco tiles lit by sunshine from the bay - was appealingly authentic, the luxe factor was compromised by an oversized cedarwood steam cabinet with a tiny head hole that looked like the crude torture apparatus of a silent-movie villain (albeit one with excellent carpentry skills).

With trepidation, I clambered in, lowering myself on to the wooden bench where four generations of rheumaticky farmers had rested their aching buttocks. A wooden lever by my hip controlled the flow. I gave a tentative tug and a whisp of steam snaked from my ankles to my neck. Fantastic! Five minutes and my pores were opened and ready for the bath; my mind a little less so.

The tub had been filled with seaweed - and we weren't talking about a few fronds here. Lurking in the brown, iodine-tinted water was an undulating mass of plant matter. A pungent smell - half salty ocean, half well-seasoned wakame soup - rose from the surface.

Slipping - literally - into the hot water (the seaweed had released a substance the consistency of olive oil) all doubts disappeared. Silky-slimy strands stroked and tickled, and the saltwater created an irresistible buoyancy. There was no sign of any sea life - although Christine had confided that some French visitors ask for a few periwinkles to be sneaked through the filter so they can snack as they soak. And there was no time limit. Hours might have passed, with nothing to break the peace but the gentle lapping of seawater - and the faint whimpers of bathers as they braved the last stage: a tankful of icy Atlantic water released from overhead.

I wimped out and stayed warm. Later, dried off and feeling fabulous, I walked up the road for a spot of fossil-hunting. Hunched on the beach in a warm drizzle, torn between admiring pebbles ingrained with prawns and razor shells, and the newly silken hands that held them, I toyed with dinner plans. Was it to be inland to old-fashioned Ballina for wild salmon and mushy pea purée at Crockets on the quay; or south along the coast to upmarket Westport, where weekending Dubliners pack the waterfront seafood restaurants? Something with crab suddenly appealed.

Calling in to say goodbye to Christine, I noticed she'd displayed magazine articles on the walls about seaweed-therapy holidays that cost £1,000-plus. At Kilcullen's Seaweed Baths, a steam and a soak costs just under £10. As she waved me off, she said: "Visitors often say this is one of the best experiences of their lives, but it can't be that good, can it?" Well, maybe just the best bath ever.

For more information, contact the Irish Tourist Board (0800 039 7000).

Destination guide: Ireland