Work Out on Water, yoga on the Cook Islands review: A balancing act

Did you hear the one about the guy who tried yoga once at his local gym, figured downward dog and cat stretch poses weren't rocket science, so signed himself up to join a yoga retreat in the Cook Islands with five expert ... and very beautiful, yoga devotees (most of whom do yoga once a day)? No, you wouldn't have, 'cause I'm that guy; and I'm only ready to talk about it now ... OK? So listen up; 'cause it gets worse, for this won't be any old yoga retreat where one might retreat to the back of the class and hope no one sees one's distressing attempts to touch one's toes. No, this yoga retreat's done entirely on water – indeed on one of the South Pacific's most pristine lagoons – I'll be forward folding, dolphin planking, high lunging, low lunging ... even attempting a Half Lord Of The Fishes and a One-Legged King Pigeon pose all on top of a stand-up paddleboard (SUP) (something, incidentally, I've also only tried once before) with nowhere to hide.

"Don't worry about it," Work Out On Water's owner (and chief yoga instructor) Charlotte Piho reassures me when I first meet her at Aitutaki's tiny airport, 40 minutes flight time north of Rarotonga. "Last time we had a total beginner he was doing headstands on the board by the end of the week." Piho hails from the Cook Islands, she's run yoga retreats all over Europe and California – even in Singapore - but says nothing beats doing them at home. "Could you imagine a better place for a yoga retreat?" she asks rhetorically right on cue as we round a corner and see the island's famous blue lagoon for the first time. Her father, Tuhe, is her assistant for the week. All week he'll attend to our every need bare-chested, climbing coconut trees to bring us coconut nui after each yoga session, dragging SUPs aboard boats and onto planes and across lagoons; and cooking local delicacies like ika mata (raw fish marinated in lime and coconut milk with carrot, onion and capsicum) when we're tired, sunburnt and our bodies are stretched out as far as they'll possibly go.

While the retreat begins and ends in the warm, clear waters of Rarotonga's Muri Lagoon, the highlight is the three days we'll spend striking yoga poses atop Aitutaki's gigantic lagoon. For this is arguably the world's prettiest lagoon, only Bora Bora's world-famous lagoon can possibly top it for sheer star power (and unworldly iridescence), but Bora Bora's lagoon is straddled by hundreds of over-water bungalows. Aitutaki's equilateral triangle-shaped lagoon is home to just one low-key retreat – the other tiny isles (motus) that sit in Aitutaki's lagoon are blissfully devoid of any development at all.

We'll be reaching the outer reaches of the lagoon aboard a boat – to a motu called One Foot Island. From here it's a short paddle to a sand spit dubbed Heavenly. When we reach it, we'll have the entire lagoon to ourselves, and to save us from drifting away to the barrier reef that protects us here, we'll anchor ourselves a few metres apart where the spit falls down to the depths below, filling green canvas shopping bags with sand and attaching them to our leg ropes.

Sounds blissful, doesn't it? Well, just hold your horses, now's the time we're forced to contort our bodies into positions from which they may never return. Anyone who doubts the effects two decades of regular snowboarding can have on the human torso should be beside me right now. We start simply enough, the Pacific sun shines down on me as I assume the lotus position, shutting my eyes and bringing my hands to my heart ... easy. I grab the rails of my SUP as I stretch my body full-length, ignoring the first audible cracks my body makes. But it's when the poses begin to get more intricate that my board seems to shrink in length, till it tilts and teeters with every single movement I make. It's quarter way through my first sideways plank as my arms and side begin to tremble that I topple right over. It's all I can do to get back onboard, the water's at least 25 degrees and with my polarised sunglasses on I count at least 10 shades of blue. There's no prettier yoga studio anywhere on Earth, the sun radiates off the milk-white sand of the spit, across the still water, and down from a cloudless ink-blue sky.

Thirty minutes in and the poses begin to move beyond angles I could ever twist myself into (Piho adjusts her sessions to ensure everyone's ability is matched). "Now we'll try a bridge pose," Piho says. I straighten my back, push both arms out and lift myself up off my board. Around me, others fold their necks entirely under their torsos; forming a human bridge as steady-looking as Sydney's famous landmark. But I'm content instead to lie on my board and take in my surroundings, watching a turtle poke its head out from all the turquoise, noticing tiny white tropicbirds with their distinctive long tail circle above me in the Pacific sky.

While yoga is the main focus here, there's much more to Piho's retreats. One day we paddle the entire 18-kilometre journey back from One Foot Island to the mainland, other days we take hikes through Rarotonga's forested, mountainous hinterland or visit the island's weekly markets. In Rarotonga we stay at Piho's family home – where Tuhe tends to a backyard teeming with tropical fruits and ruled by noisy roosters. There's an obvious homespun appeal to Piho's retreat that makes me feel as if I'm staying with friends or long-lost family, rather than being here on vacation.