Birch branches slapping bare skin - would you dare try this wellness ritual?

As the sharp sound of birch branches slapping bare skin fills the sauna, I'm starting to wonder what I've done. I knew our Nordic Bathing Ritual in Viking Jupiter's LivNordic spa was going to involve steamy times in the sauna and cold snaps in the snow grotto, but now that the spa therapist has moved onto thwacking us, I'm not the only one with an alarmed look on my face.

When it's my turn, I go from pre-flinching to wide smiling when I discover just how good it feels. The leaves are soft and the birch scent smells so good in the hot sauna air. And as I realise I'll jump at the chance to do it again on land, I know I'll always remember my first time at sea.

While some may prefer old faithful massages and facials, when I visit a cruise spa, my eyes go straight to the things I can't do any old where. Happily, my last 20 or so years of cruising has seen an increase in refreshingly unexpected treatments as cruise spas grow in both popularity and variety.

Cruise Lines International Association managing director in Australasia, Joel Katz, says the evolution of on-board spas has come as cruise companies invest heavily in on-ship experiences.

"It's now common to find high-end spa centres and extensive wellness facilities on board many ships, particularly among luxury cruise lines, which are enjoying very strong demand at the moment."

Eight years ago when I spied an Amethyst Crystal Sound Bath Healing treatment on Silversea's Silver Muse my curiosity was piqued. "You're the first person to ever try it," the spa manager smiled as she showed me the quartz crystal bowls she'd play. And as those sounds reverberated around the room the wow factor was real as I felt waves of new sensations on the amethyst crystal panel bed.

In recent years more cruise ships have added experiences for the woo-woo curious. Oceania Cruises spas have amber and quartz crystal beds while on Regent Seven Seas, amber and quartz poultices join massages for a vibrational energy boost. At Celebrity Cruises' Edge Series spas you can feel the amethyst vibes in the Crystalarium Energy Healing thermal suite, and Himalayan Salt Cave rooms are popping up on Explora Journeys' ships, where you can lie back and breathe the mineral-rich air.

While I would happily do Viking's Nordic Bathing Ritual anywhere in the world, I love experiences with a sense of place, which is why it was all the better for being in Scandinavia. On a Ganges cruise with Uniworld, I went straight for the spa's Ayurvedic Retreat. Knowing I was on India's sacred river added an extra element to the dry herbal powder body scrub, heated cloth boluses filled with ayurvedic leaves and Abhyangam massage to retune my energy cycles. Meanwhile on a Blue Lagoon cruise in Fiji my traditional Fijian Bobo massage would have felt special enough on the ship but was even better on the beach from The Blue Lagoon movie as I listened to the rhythm of gentle waves meeting soft sand.

Katz says that as the growing trend towards health and wellness holidays continues, we can expect to find even more ways to be pampered at sea. "Travellers are increasingly focussed on the experiences they have when they cruise, and many cruise lines have responded with more extensive spa facilities, a greater range of treatments and a more holistic approach to wellness."

If you like to sweat it out, Norwegian Cruise Line's Prima and Prima Plus class ships now have clay saunas where guests apply mineral-rich clay to their skin before heating up, while on a Scenic Eclipse Wellness Cruise you can be covered in enzyme-rich honey as part of a sauna ritual. MSC's Aurea Spas are adding Kneipp Paths, where you walk through shallow hot and cold pools to stimulate lymphatic circulation and the immune system.

Along with an increase in medispas if you fancy some microneedling and dermal filling at sea, some ships including Virgin Voyages offer IV hydration therapy where your intravenous pick-me-ups include vitamins and nutrient cocktails to keep you powering on.

Personally I'll stick to being hit with twigs and trying the latest crystal-infused massage. But hey, each to their spa-day own.