Well this is a first. Im pretty sure I've never been butt-naked before, wallowing in the pipping hot waters of an exposed white bath, perched on a timber-deck platform gazing over one of the most beautiful, unspoilt coastlines of Australia.
Sure, the water in the bath is a bit grubby. But that's because I've opted for the signature Tasmanian Peat Bath therapy.

Cecilia, the resident Polynesian masseur at the new spa complex which has opened this spring at the Bay of Fires Lodge, has shown me the bowl of grey paste which is a mixture of peat and the essential oils of sandalwood, neroli, sage and grapefruit. Tasmanian peat, she explains, is rich in proteins, trace elements and minerals and is an excellent skin hydrator.

Then, after stirring it into the bath water, she leaves me alone to enjoy the serenity and privacy of this sublime bathing pavilion.

For the past three days, our group (three couples from Newcastle, a mother and daughter from Melbourne, plus myself) has been trekking along the exquisite but drainingly soft white sands of Tasmania's spectacular Bay of Fires (so named in 1773 by Captain Tobias Furneaux because of the large number of aboriginal fires sighted as he sailed by).

Earlier today, we had taken to kayaks, battling a stiff headwind as we paddled our way across the pretty lagoon that is Ansons Bay. So I feel this 30-minute indulgence has been well-earned.

From the bathtub, I can see many of the landmarks our trekking party has visited since we set off from Stumpy's Bay at the north of Mt William National Park on Tasmania's east coast.

As I sip a cup of rose-coloured Yulu tea and soak in the luxurious waters, it is an ideal time to reflect on the journey we've made under the expert tutelage of our two multi-skilled guides, Ed and Hannah.

Statistically, it doesn't sound very arduous. By the time we finish at lunchtime tomorrow, we'll have walked around 35 kms, mainly along the national park's many beaches but with a few boulder scrambles and inland deviations through pristine wilderness thrown in.

Of the seven guided treks that are collectively marketed as Great Walks of Australia, the Bay of Fires Walk has easily the gentlest profile. Yet our group is exhausted - in the best sense of the word as mind and body, senses and imagination have been satiated.

The Tasmanian Walking Company - which runs both the Cradle Mountain Huts Walk and the Bay of Fires Lodge Walk - is one of the pioneers of 'eco-luxe' touring in Australia and this guided four-day trek has been operating since 1999. However, as of September 2013, the company has new owners - Brett Godfrey and Rob Sherrard (two of the founders of Virgin Australia).

The company's marketing pitch is'uncomplicated luxury', and the phrase fits. The formula is simple: great food, fine wines, eco-friendly accommodation and intelligent, personable guides who are equally at home identifying animal tracks and edible plants as they are creating fabulous cuisine.

On the first day, we'd walked the nine kms from Stumpy's Bay, past Boulder Point and along Cod Bay to Forester Beach Camp, tucked away from the sea breezes in the sand dunes. There Hannah and Ed had surprised us all by rustling up a superb dinner of barbecued Tasmania salmon, Vietnamese noodle salad and chocolate mousse, all washed down with local wines - Holm Oak pinot noir and Three Wishes riesling.

After a comfortable night spent under canvas in permanent huts each sleeping two walkers, we'd enjoyed pancakes for breakfast before setting off on the 16 km trek to the architecturally superb Bay of Fires Lodge, set on 35 hectares of private land and with breathtaking views of the Tasman Sea.

Soon after leaving Forester Beach Camp, the track left the beach to meander through a series of 'marsupial lawns' behind the dunes. At the first of the ponds, Ed had explained how the ponds have formed over granite, flooding each winter to create clearings among the tea trees - a perfect habit for wombats, wallabies and quolls. We learn why wombat poo is square, listened for Banjo frogs, and tasted native spinach and other edible plants.

Back on the beach, the highly enjoyable lessons continued. Hannah had picked up a brown cucumber-shaped pod with a stringy tail out of the sand: what is it? When no-one guessed, she revealed it was the discarded egg pod of a Draughtboard shark. A bit later, she picked up the familiar shape of a dead cuttlefish and showed how we can tell what kind of trauma it has experienced during its life by 'reading' the ink rings on its shell.

For all the gourmet tastes (those home-baked cakes and perfectly poached breakfast eggs!), the beautifully appointed accommodation, even the gorgeous new spa, it is the trekking experience itself that is most memorable about this Bay of Fires walk - and all nine of us in our party feel enriched by the knowledge our guides share along the way.

And yet, it sure helps that the Lodge - with its cantilevered deck, soaring roof, eco-friendly showers, small library and welcoming lounge/dining room - is such a special place. Now that the spa and that alfresco bathing pavilion have been added to the mix, it is a destination of distinction. Even if it is a bit of a trek to get to!

Check in: Bay of Fires Lodge, Mt William National Park, East Coast TAS 7264. (03) 6392 2211
Ultimate Luxury: The range of treatments at the Bay of Fires Lodge Spa incorporating Li'Tya products.
Most Indulgent Moment: Sipping Yulu tea while taking open air Tasmanian peat bath.
The Little Things: Freshly home-baked cakes after each day's walk.
Junior Luxies: Minimum age, 12.
Dress code: Good boots, sensible walking clothes plus smart casual for dinner.
Dent in the platinum: 4 Day guided walk from $2150 per person, twin share. Single supplement by prior arrangement.
Luxury Resorts Link: www.bayoffires.com.au