There are monsters of the deep in the big blue lagoon. We lean over the sides of the lurching boat and watch for black shadows. Is that one? No, that's just the Rorschach blot of a passing cloud, tempting our imagination. There! No, a turtle, paddling disinterestedly onwards as we hoot in excitement. To the turtle we must seem like disorderly angels, shimmering and floating somewhere above, our cries subdued by the water.
Out boat lurches across Moorea's pellucid lagoon like an ungainly water beetle. We're afloat in a palette of aquamarine and cobalt and eye-scrunching electric blue. The island's crumpled mountains are an astonishing apparition in this endless ocean, sitting in skirts of reefs against which the surf booms.
For the moment, though, we're ignoring French Polynesia's staggering beauty. We remain on monster watch, eyes down. A dark shadow passes, a black hole torn in the fabric of the sapphire sea. Was that it? Yes! The shadow turns and glides back towards us. There's a collective gasp. This is a monster of unexpected size. Bigger than the turtle. Perhaps as long as a human, but of indeterminate shape and blurred edges. Phantasmagorical, like the creatures imagined by early map makers.
I'm sailing with Crystal Cruises from Papeete to Auckland and, only one day out from our departure port, am on a shore excursion promising an encounter with stingrays. Not that we're ever on shore. Crystal Symphony is anchored in Opunohu Bay in Moorea lagoon, and we're decanted into a small local boat and puttering off towards our stingray experience in no time.
Now we are seeing not one or two stingrays, but a shoal of them. Or maybe a flock. It's like an upside-down world in which creatures fly beneath the water. There are a half-dozen stingrays now and, as our boat slows, their blurred outlines solidify. The stingrays don't so much fly as undulate on giant wings like Yves Rossy, the Swiss wingsuit adventurer.
The boat putters to a halt in water so clear we seem to be held up on nothing. The stingrays circle like fragments of a disturbing dream. Our local tour guide, Tom, doesn't seem perturbed. We should get into the water, he says, and swim. The stringrays won't mind.
We give each other sideways glances, and mutter, and drag on our snorkelling gear slowly, hoping someone else will take the plunge first. Then I find myself standing on a sandbank in warm, waist-deep water. Stingrays circle. Some of my fellow shipmates scream. Tom laughs. There's nothing, apparently, to fear except out own atavistic nervousness.
The stingrays are the size of half a bedsheet, sleek grey above, white below. Their tails are the length of my arm. They seem harmless enough, though. A bit spacey, but curious. They swim right up to Tom, lured by octopus bait. They push delicately between us, wobbling their wings like ballerinas' tutus.
Slowly I relax. I don my mask, sink to the lagoon bottom and watch stingrays fly over me, outlined like stealth bombers in the big blue. You can touch them, says Tom. Their wings – more properly, pectoral fins – are strangely rubbery and slightly slimy, like wet mushrooms.
You have to revert to terrestrial comparisons in this watery world beyond your normal experience. Later I'll see fish named after scorpions and trumpets, angels and butterflies, peacocks and Moorish idols. The names capture their exoticism and bright, banded colours, but are never appropriate. Yet what other references are there? What can you say about the lagoon's corals, except that they blossom like roses and antlers and synthetic Christmas trees?
But the stingrays – black, almost shapeless, unappealingly named – steal the show among all these flamboyant, show-off creatures, thanks to their size, ethereal motion and silence. You can hear fish chomping on coral with a sound like fingers scratching gravel. You can hear the sobbing of the tide on the outer reef, pulsing in your underwater ears. But the stingrays sidle up to you unannounced, flapping past with a silent slap of leathery wings. They seem anxious as we leave. They trail us to the boat's ladder. One heaves up over a snorkeller's back like a cloak, as if trying to drag him back into the lagoon. Then we up anchor, and the stringrays escort us for a while, flitting black shadows again, friendlier monsters of the deep than we had imagined, and seemingly despondent that their day's entertainment is sailing away.
What's so special about such animal encounters? They make you smile. Your skin prickles. They make the world become still, and nothing matters but the here-and-now wonder of it all. You're a child again. You feel at one with nature, you're awed and astonished. These are the sorts of moments you journey for, when the banalities of travel are overcome in an instant by something extraordinary.
Happy chatter propels us back onto Crystal Symphony. I shower off the salt and head up to Palm Court, wedged high on the front of the ship. Its marble and Murano glass shimmer like the lagoon. Over the tinkle of teacups and scones we're still talking about our stingrays. Tomorrow we're in Bora Bora, and some of us will relive the moment all over again.
For now, Moorea looms through Palm Court's vast windows. Opunohu Bay is one of the most beautiful corners of the earth. Its jagged peaks rise above a fiord-like inlet, a backdrop to an improbable Hollywood musical.
We sail out of a channel in the reef so narrow that breaking waves form skirts on either side of the ship. The late afternoon sun throws even more colour across the lagoon, azure and indigo and turquoise. Somewhere beneath, the stingrays are swimming.
How happy I am to be on a cruise ship at the start of a journey, with many more days ahead.
This Papeete-to-Auckland sailing with Crystal Cruises has several other shore excursions that showcase the Pacific's most brilliant lagoons and scenic harbours.
Ukuleles twang and the boat crew sings as you're taken across Bora Bora's deservedly famous lagoon for another wade-in with stingrays, and an equally thrilling encounter with black-tipped reef sharks. Then you head to a motu (sand island) where you can impress your footprints on white sand and admire views towards Bora Bora's cloud-wreathed peaks.
The vast lagoon in this low-key Cook Islands destination is 45 kilometres around and sprinkled with tiny motus. A Crystal Cruises shore excursion takes you to Maina Sandbar, where you can wade amid giant clams and tropical fish, and One Foot Island, surely one of the most beautiful spots in the Pacific. The blue shades of the lagoon are astounding.
The Cook Islands' main island rears forest-clad mountains from an effervescence of reefs. The narrow encircling lagoon looks magnificent from afar, as you'll discover on a Rarotonga by Jeep excursion that climbs hillsides for dramatic views over the island. The eggshell blue of the lagoon contrasts magnificently with the dark-blue open water beyond the reef.
The sail into this hidden harbour, between wild beaches and an extinct volcanic cone (Mauao) is sumptuous, so be sure to stride the decks. The chief attraction of this New Zealand port isn't the city itself but the attractive beach suburb of Mount Maunganui, where cruise ships dock. A terrific walk straight off the ship circumnavigates Mauao to ocean-side beaches.
The most thrilling shore-excursion option is a sailing experience on an America's Cup yacht. After a safety briefing, you're out on the water being shown the ropes, quite literally. Then you're off and racing. The yacht surges forward, spray hisses and sails crack. No better way to experience the harbour setting of New Zealand's premier city.
Crystal Cruises sails various itineraries in the Pacific. Among them is a 13-night Los Angeles-to-Papeete cruise departing January 22, 2020, that visits Nuku Hiva, Rangiroa, Bora Bora and Moorea in French Polynesia, priced from $US5214 a person (about $7322) including all meals, wines and spirits, Wi-Fi, entertainment and gratuities. A 2.5-hour Moorea Private Snorkelling Safari shore excursion costs $US109. Phone 1300 059 260. See crystalcruises.com
Brian Johnston travelled as a guest of Crystal Cruises.