It looked sinister but it was utterly intoxicating. As the snake slithered across the ocean floor we couldn’t help but be mesmerised as we hovered a safe 3m above it, trying to keep up while breathing heavily into our snorkel gear.
As it moved, the snake’s black and white body disappeared under flurries of sand, a performance worthy of the balmy colosseum of the Pacific Ocean off Vanuatu.
We followed it in awe, trying to distract it with shadow puppets and by diving for an up-close inspection - a move that requires the snorkeller to exhale strongly.
As the more bold among us snapped away with a camera, the snake became uneasy and quickly fled, flicking sand in its wake in the equivalent of a middle-finger gesture.
No matter. There were countless other underwater treasures in Vanuatu, such as a giant turtle, camouflaged by coral, motionless as fish leisurely cleaned the algae of its olive-green and dark-spotted shell. For us, a spectacle. For the fish, a mobile restaurant.
Moments earlier, a similar turtle glanced our way as its body, the size of a large coffee table, soared through the ocean sky, sleepy flippers propelling it along deceptively quickly.
It dived effortlessly until out of sight - quite some way in the crystal-clear waters off Hawk Island, one of Vanuatu’s 80 or so smaller islands spread across 450,000 square kilometres of ocean.
The country, with four main islands forming a Y-shaped chain, is ripe for exploring both on and offshore. Each island offers golden-sand beaches bordering dense bush.
The population is about 200,000, but about 15 of the islands are uninhabited.
The island shores are the enginerooms of the economy - tourism, mainly luxury island resorts, is rivalling agriculture as the main source of the country’s wealth. And there is much on offer - sea-kayaking, diving, beach-lazing. But snorkelling is the least intimidating way to unlock the secrets below the waterline.
We snorkelled past desert-like patches of ocean-bed and came upon colourful, vibrant jungles of coral that resembled a buzzing underwater metropolis: blood-red discs sitting atop each other, looking like a futuristic building; dense shrubs of purple, green and bursting-blue sea urchins and throbbing spheres of brain-like texture that seem to police the sea-city highways.
And, like a busy and ethnically diverse city, the fish population seemed to have a class structure: some are rainbow-coloured hippy fish, others resemble tigers or bumblebees. And there are schools of tiny pale white fish - clearly the oppressed class - and stylish, executive fish clad in black and white cocktail dresses.
They crowded around the coral, oblivious as we watched wide-eyed.
In the darker depths of the city, a white sea worm protruded its single tentacle in search of food, quickly retracting when it came across something unfriendly.
A ray, its majestic charcoal wings as magnetic as they were menacing, disappeared as soon as it was spotted.
Clams of all sizes - the biggest as large as suitcases - cluttered the seabed among bright blue starfish that seemed to improve in brightness the longer you stared.
Earlier, a group of us were taken on a leisurely sea kayak voyage up Malo River to a swimming hole, where relaxation was the order of the day.
Some snorkelled while others swam and soaked up the harsh summer rays. The more adventurous hurled themselves off tree branches into the watery abyss below.
The pure colour of the river, which was lined with dense bush and coconut palms, presented a paradise that we had to ourselves.
The excursion is exclusive to Bokissa Eco Island - we called it Honeymoon Island because just about everyone went about in couples - which lies a bumpy 45-minute ride across the ocean from the country’s biggest island, Espiritu Santo.
The scattered islands of Vanuatu means much of the population have maintained their own distinctive cultures. Vanuatu has 115 languages. That’s including English and French, remnants of its colonial past until independence in 1980.
English-speaking visitors may be forgiven for thinking the local dialect seems vaguely familiar. Bismala, a pidgin fusion of English, French and local language is relatively easy to read. You can even pick up phrase or two - "Fankutoomus", for example, meaning "thank you very much". But hearing it is likely to leave you none the wiser - the local lingo sounds like a single, neverending word spoken in lightning quick time.
This contrasts with what is known as island time, the casual, laid-back way of going about things.
Island time is not often the best ingredient for making dollars, which can frustrate foreigners hoping to do business.
Despite this, there is a buzz about Port Vila - the boys that hurl themselves from the wharf into the water, the barefooted soccer games in makeshift playing fields of dry dirt or overgrown grass.
In the centre of town you’ll find people selling their own produce at the 24-hour market.
Island women sashay casually along the streets or stand at their stations in the market, many wearing floral dresses of vibrant colours.
They may seem hesitant to make eye-contact, but are always quick to return a smile, assuring you that the Vanuatu experience has plenty to offer, both below and above the waterline.
* Derek Cheng travelled to Vanuatu courtesy of Air New Zealand
Air New Zealand flies to Vanuatu once a week departing on a Sunday. Seven night holiday packages start from $1299 each, twin-share, from Auckland.
For details, call 0800 737 000, visit your nearest Air New Zealand Holidays Store, or visit Bokissa Eco Island is at airnewzealand.co.nz.
Where to stay
Bokissa Eco Island is at www.bokissa.vu.
Vanuatu Tourism is at www.vanuatutourism.com