The collective noun for sharks is, apparently, a shiver. It's not a word I expected to use in a tropical lagoon but, surrounded by more than a dozen of them circling so close that they actually brushed my skin, it was the perfect fit. And not just sharks: stingrays too, a metre across, trailing their stiff and treacherous tails. It was all exactly what had been ordered.

"Tahiti's not just about honeymooners lying on beaches," I'd been told. "Try the exciting activities! Get adventurous!"

So here I was, neck-deep in Moorea's lagoon on an excursion that had promised ray and shark feeding, hoping not to be part of the menu. "They're just black-tipped reef sharks," guide Stefan tutted. "They don't bite. But don't touch the rays' tails," he added unnecessarily before slipping into the water to be mobbed by a handful of them, boisterous as puppies.

Trusting in the safety of numbers, the 50 of us on the catamaran followed him in, to discover at once that rays feel soft and smooth, like an old rubber spatula, and are about as threatening. All our shrieks were of pure delight, and an hour whizzed by before we reluctantly climbed out again to go for our island picnic - though the sharks' feeding frenzy as they finally got the fish-scramble they'd been waiting for made us feel better about leaving the water.

Fooling about on the surface was one thing. Walking on the lagoon floor with a couple of metres of water above my head was quite another. Breathing underwater is clearly unnatural; being able to do it with a dry face is just weird. Once I'd taken the leap of faith into the lagoon, though, it turned out to be the best sort of weird: breathing normally, with Aquablue's bright yellow diving helmet perched on my shoulders, I could slo-mo across the bottom like a marine astronaut.

The sun, shining through crystal-clear water, made shifting patterns on the sand, cartoon-bright fish flitted around me and more rays glided up, attracted by the cylinder of food I held. Able to wear my glasses, I could see it all perfectly, and I wasn't the only one to be thrilled: "That was brilliant!" enthused a man with 20 years' scuba experience. "I've never seen the fish so clearly!"

The next day there was too much wind for my stand-up paddleboard expedition: two hours-plus of dip and pull, dip and pull across the lagoon and back again colour me disappointed. Not. But I did get to scoot around the sheltered canals of Moorea's Intercontinental hotel, ducking under bridges and feeling superior to people sprawled on their balcony loungers.

The day's real workout came aboard an ATV, bouncing over potholed roads and then along dirt tracks through the bush. These quad bikes look like fun - and they are - but they're heavy and cornering takes some effort, especially at our initially slow speeds. Our leader Guillaume gradually extended us as we gained confidence, and before long we were splashing through fords and even catching air, careering over banks as he took us on a three-hour tour of the island's inner fruit bowl and high lookouts. Our courage was rewarded with spectacular views of jagged peaks above and reef-edged coastline below - and after meeting a car on the narrow track up to the top of Magic Mountain with its precipitous drop-off, we really felt we'd earned it.

Guillaume pointed out a razor-edged ridge rising to a peak across the bay. "You could climb that track," he said. "Even better views!" Next time, maybe.

By Pamela Wade  www.nzherald.co.nz