The fantasy Pacific island guarded by a 'wall' of sharks

Dubrovnik has its imposing city wall. Buckingham Palace has its wrought iron fence. But, a tiny island in French Polynesia has, perhaps, the best ‘wall’ of all: hundreds of sharks patrolling the lagoon entrance.

When you think of French Polynesia, an image of Bora Bora's idyllic lagoon pops to mind.

But this country is so much more. It has 130 islands spread over a vast distance with an exclusive economic zone (essentially a sea boundary) more than double the size of Western Europe, and I'm about to share two secret spots within that.

To reach these islands, we're aboard a Regent Seven Seas cruise ship travelling from Hawaii to Papeete. The first four days involve sailing towards French Polynesia before coming across a remarkable island.

Welcome to the Marquesas Islands, an archipelago of 15 remote islands that feel like the middle of nowhere. And that's because it's true. This island group is the furthest away from a continental landmass anywhere in the world.

The islands were formed over millions of years from volcanic activity, leading to a lush landscape that has remained largely untouched by the modern world.

Many visitors come by cruise ship because the island is 1400 kilometres from the capital, Papeete. To put that into a New Zealand context, it's roughly the distance from Cape Reinga to Bluff and takes more than three hours on an Air Tahiti turbo-prop plane.

Tourists also visit on the Aranui 5, a dual-purpose cargo and cruise ship that does a two-week rotation of the country's outer islands.

Whatever way you get there, it looks like a place dinosaurs could still be roaming. The island has a mountainous interior lined with deep valleys that are densely forested thanks to ancient volcanic soil. It's all surrounded by perfectly turquoise waters.

Once on the island, there is lots to keep you occupied. One of the more famous stops is the Hakaui Valley which is home to an enormous waterfall - higher than Auckland's Sky Tower.

If you're lucky enough to be staying a couple of days, you'll have lots of isolated beaches to explore, jungle walks, and the remnants of ancient marae to look at. The snorkelling is also excellent, with lots of colourful fish, turtles and even manta rays.

Because of its isolation, the island's traditional culture survives today, making it the perfect place for those who enjoy getting well off the beaten track for a holiday rich in adventure and culture.

If, however, you prefer soaking in the sun on a beach, you're better off heading to our second destination, Fakarava.

After two days sailing further south, we reached one of the golden jewels of French Polynesia, Fakarava. This idyllic 60-kilometre strip of sand is surrounded by some of the dreamiest waters in French Polynesia. Unlike Nuku Hiva, which has a mountain more than a kilometre high, the highest point in Fakarava is just a metre above sea level.

The island is part of the Tuamotu Archipelago, a chain of more than 70 low-lying coral atolls. The beauty rivals Bora Bora, without the crowds.

Rent a bicycle and pedal yourself to a secluded beach; they aren't hard to find. It's also not hard to find sharks - because the island and surrounding ocean is relatively untouched by humans, the waters teem with life. The island has even been named a Unesco Biosphere Reserve because of the incredible array of species inhabiting its coral reefs.

, with 250 to 700 grey reef sharks documented in the channel entrance to the atoll.

It's thought they rest here during the day, using the currents to keep afloat, and by night the channel becomes a feeding frenzy. The sharks are so tightly packed, it’s been described as a ‘wall’ and the highest concentration of grey reef sharks ever recorded.

If you're a keen diver, operators on the island will take you to see the spectacle. But you don't need to be a diver to experience sharks - our first encounter came when we were waist-deep in the lagoon.

We saw a black shadow a few hundred metres away, which slowly swam closer. It turned out to be a nurse shark, which are a little like Labradors of the lagoon, and pop by out of curiosity. After a while, you get very used to seeing sharks.

Like Nuku Hiva, the island doesn't have any big chain hotels - instead, it has guesthouses and a lodge with beach bungalow-type accommodation. This only adds to the sense of isolation.

The island is only home to about 800 people, and most are found in the main village of Rotoava. It has just a few streets, alongside a couple of churches and stores.

There is also a pearl farm you can visit, and a coconut oil factory. But the real reason to put this island on your bucket list is for diving and snorkelling. If you want to see a glimpse of what the ocean looked like before humans arrived, this is one of the best places to in the world to experience it.

Regent Seven Seas offers an 18-night trip from San Francisco to Papeete, which includes Hawaii, Nuku Hiva and Fakarava from $22,030 per person. It also has 10-night French Polynesia cruises that includes Nuku Hiva and Fakarava from $9690. See:

Air NZ and Air Tahiti Nui have regular flights from Auckland. Air Tahiti and Moana Air offer domestic connections from Papeete to Nuku Hiva, while Air Tahiti has connections from Papeete to Fakarava.

Flying generates carbon emissions. To reduce your impact, consider other ways of travelling, amalgamate your trips, and when you need to fly, consider offsetting emissions.