Paul Rush follows a trail of bubbles to Champagne Beach on Vanuatu's largest island.
The island of Espiritu Santo is "the sleeping giant of Vanuatu", says our guide.
"Travellers haven't woken up to the diversity of adventure experiences on this beautiful, unspoiled island."
From the lush tropical gardens of the Coral Quays Fish and Dive Resort it's a short run to the wide main street of Luganville, the only town on "Santo". It's hard to imagine that this little cluster of weathered concrete shops and offices accommodated 100,000 American troops during World War II in its role as the major staging post for the Pacific.
Our first stop on this round-island journey is Million Dollar Point, named after the millions of dollars worth of equipment disposed of there.
After the war, United States Army generals offered redundant earthmoving machinery to the Vanuatu government at one 10th of its value. The shrewd officials turned the offer down, gambling that the equipment would be left behind anyway.
The US reaction was swift and extreme: all the General Motors trucks, bulldozers and forklifts were swung by cranes into deep water.
Later, during an illegal salvage mission, a steel coastal trading vessel was moored above the watery graveyard of machinery. The crew had miscalculated the tidal variation and the ship impaled itself on the equipment and sunk into the depths.
Santo feels something like a Wild West frontier as we negotiate the narrow, pot-holed coral road up the east coast towards the village of Hog Harbour.
A short diversion into the jungle brings us to the wreckage of an American B-17 "Flying Fortress" heavy bomber aircraft.
The remnants of the aircraft is spread over a hectare of forest. A wing section has numerous rectangular holes where local Ni-Vanuatu fishermen have removed aluminium strips to repair their boats: an eco-friendly recycling project 70 years in the making.
We pass family groups who smile and wave to us in a natural, unassuming way. Children skip along beside mothers wearing bright, floral Mother Hubbard-style dresses. Men carry loads of taro, yams and the precious kava root that can be squeezed and filtered into a potent liquid that tingles in the mouth, numbs the lips and makes the imbiber sublimely languid and content.
The Nanda Blue Hole, a freshwater spring bubbling up through old coral beds, is our next stop. The crystal-clear, azure blue pool is overlooked by a large banyan tree and festooned with a laughing gaggle of local village boys and girls, who are daring each other to leap 6m off an overhanging branch. We join in the fun, donning snorkels and masks to explore the pool.
Using gestures, I demonstrate the use of a snorkel to our Japanese traveller. She does a complete circuit of the Blue Hole with the apparatus, breathing in through the snorkel and exhaling vigorously with every breath. Sometimes sign language doesn't quite do the trick.
On the road north, we catch glimpses of sheltered coves lapped by a gentle sea of exquisite turquoise.
Further out, barely distinguishable in a bubble of tropical haze, is the island of Ambae that inspired author James A. Michener to write his classic work of related short stories Tales of the South Pacific, which spawned the famous Broadway musical South Pacific.
Champagne Beach truly deserves its reputation as one of the world's finest beaches.
The small, crescent-shaped bay is sheltered by a prominent reef and the outlying islands. The sand is a delicate powder of crushed coral that squeaks under your toes like pure sugar.
I have experienced only part of what the magical island of Espiritu Santo has to offer. The secret to enjoying its treasures is to go with the flow, like the Ni-Vanuatuans do.
Climate: The dry season (May to October) has an average temperature of 23C. The green season, from November to April, averages 28C.
Further information: See vanuatu.travel.
Paul Rush travelled courtesy of Tourism Vanuatu and Air Vanuatu.