In the silent blue depths of the Fijian coral reef, having my hand grabbed by the diver next to me was the tactile equivalent of a shout in the ear.
The diver happened to be my husband and the signal he was urgently passing on was the presence of a green turtle swimming just metres away from us.
The turtle lazily crossed our path and glanced at us with glassy black eyes before disappearing around the corner of a coral-covered outcrop. But my hand was not released from the vice-like grip my appointed dive buddy had chosen to apply.
Instead, it was yanked and pumped even harder as another creature had been spotted gracefully gliding across the sea floor below us.
It was a black-tipped reef shark moving with effortless guile some 10m away. The slow sway of its lithe grey body was enough to propel it through the water at a far greater speed than we could muster with the collective thrashing of our fins; an indication of the coiled power it held in perpetual anticipation.
Our dive trip seemed to have turned into a dive safari but without the ability to zoom off at top speed if things got hairy.
Thankfully the reef shark is virtually harmless to divers, and spotting one is just part of the pleasure of exploring the underwater world which divides and surrounds the Fijian archipelago.
Spread out across a geographical area more than twice the size of Tasmania, the islands which together form Fiji far from contain the country's natural beauty.
A greater part of the nation's bounty is to be found submerged beneath the oceans and channels which separate the beaches, forests and occasional towns of the land.
Turtles, sharks and other creatures are only a part of Fiji's marine treasures, as there is far more to explore in the pale blue light of the deep.
Spectacular coral reefs with deep canyons and natural swim-through tunnels also abound in this corner of the Pacific – plus a number of shipwrecks.
We had arrived at Matangi Private Island Resort, in the country's north-east, hoping to see just some of these marine marvels in the time we had.
As it turned out, we only needed a single day of diving. The island, located off the mainland of Taveuni, has its own dive shop and a daily program of diving for visitors who want to do more than just laze on the soft sand beaches or snooze in their traditional-style bures.
A resident Fijian divemaster accompanies guests to locally renowned sites such as the Great White Wall, and the remote location means divers are rarely sharing a site with others, which can be common to popular areas closer to Viti Levu.We had headed out that morning with not one instructor, but two. Bale was the Fijian expert, while Ally was a training instructor whose family had acquired the island as a coconut plantation before tourism became a more lucrative business.
Heading out into the open ocean, the neat rows of the trees on the higher hills had belied the island's history, and Ally had explained why so many divers were attracted to the resort.
"It's unusual for me to see any other dive boats in the places we go to – we say it's like going to your reef," she said. "We're very lucky to have all kind of reef here, with loads of soft corals, and even places where there are resident turtles."
Our marine encounter came just moments into our first dive, at a site called Broken Reef. We had descended to the edge of a circular reef with deep aisles of coral, which had been named after the fact that more exposed areas had been devastated by cyclones.
Despite its moniker, the deeper, sheltered coral was in pristine condition, and massive giant clams waited on the sea floor, like gaping mouths with iridescent gums.
After re-surfacing and changing tanks, we headed to The Wreck - a dive site with a unique tale to it.
The owners of Matangi Island had bought a boat with the idea of creating an artificial wreck by sinking it at a deep and sheltered location. They towed the boat to the island, mooring it near the shore until they decided exactly where it would be best sunk.
The only problem with the plan was that a vicious storm broke out, and the boat broke its moorings and drifted into the open ocean.
It then sank in a shallow and exposed part of the reef and has since been dismantled by a combination of strong tides and severe storms.
The engine is the only major chunk to remain intact, but sits at a depth of just a few metres – making it accessible for snorkellers as well as divers.
Other parts of the ship were strewn across the reef as we began an exploration of the site from a deeper corner. Some of it had already been covered with soft coral, which had tiny tentacles swaying in the swirling current.
We followed the trail of the wreck along the channel on a gradual incline, stopping when some piece of marine life intrigued us. There were pincushion starfish as big as footballs, a blue-spotted stingray and more giant clams.
As we reached the box-like engine in the shallowest part of the reef, the currents swirled more strongly around us. Inspecting the remnants was an ideal way of making the routine safety stop – a divers way of decompressing.
Glancing back into the deep channel, a swaying section of grey caught my eye, tipped with a corner of black. This time, it was my turn to grab my dive buddy's hand.Hold onto your dive buddy's hand in Fiji | Stuff.co.nz