The Rainforest at the Banyan Tree Spa on Koh Samui, Thailand, is a multi-stationed hydrothermal experience designed to enhance traditional therapies. The concept is similar to that embraced by the Romans; that water is the elixir of life, with healing as well as rejuvenating properties. In fact, it's surmised that the word 'spa' comes from three letters scrawled on Roman thermae walls: Salude Per Aqua, meaning 'health or healing through water'.

The 'bathhouse' concept remains popular in Europe, where 'taking the waters' became fashionable during the Jane Austen era; while the Japanese and Koreans have long appreciated a good soak. In South-East Asia, however, water therapy is still fairly unexplored territory.

Unlike most spa treatments, The Rainforest works brilliantly as a group experience. Both male and female guests are welcome to use the facility, so it's perfect for couples, friends or even families. And unlike bathhouses in other parts of the world, swimsuits are de rigueur, eliminating those uncomfortable moments of body insecurity.

The whole experience kicks off with a rude awakening - The Rainwalk, a mist-spray replicating a tropical shower, only colder. Squeal #1. From here, guests warm up in a detoxifying steam room, followed by yet another cold shower. Squeal #2. 

Back in a pre-heated 'Rasul' capsule (an Arabic-style tiled room with heated seats and herbal steam), therapists coat you head-to-toe in therapeutic mud; but just as you're feeling all warm and gooey, there's another torture chamber to shock the system - the Bucket Drench Shower. Pulling the chain to release frigid water over your searing body takes nerves of steel, despite the hope that it's doing wonders for your body. Squeal #3.

The benefits of dry heat from a sauna are well documented; and in Sweden, the best way to end a sweat is to fling yourself in the snow. But with frozen precipitation a rarity in Thailand, you'll instead be grabbed by a sweet little therapist who rubs chunks of ice all over your body. Squeal #4 - not to mention the odd bruise as you fight off your grinning torturer!

After these extremes of temperature, falling into the massive Vitality Pool is sheer relief. At last, a constant temperature, if not water pressure! The pool has several stations where jets of water massage specific parts of the body, including waterfalls for head and neck, a fire hose for the upper body, a 'lazy river' experience where you swim against the current, and a full body lounger, where you simply lie back and let the jets do their stuff. 

The session ends with a 15-minute rest on a heated lounge chair, complete with a foot massage in true Thai tradition. 

And suddenly there's silence, as guests enter that zone of total surrender...

The Rainforest Hydrothermal circuit can either be experienced on its own ($35 for 60 minutes) or combined with your choice of massage ($245 for 150 minute treatment). See banyantreespa.com.

The writer was a guest of Banyan Tree and Tourism Authority of Thailand.