First revealed to the world by 19th-century naturalist Charles Darwin, the Galapagos Islands' unusual wildlife mixture has visitors spellbound.
‘Shark!" yells out one of our group of snorkellers excitedly. "Over here!"
I can't believe that I'm swimming over for a closer look. The same alert given in Australian or New Zealand waters would result in a mass exodus from the water in sheer panic - but not so here in the clear pristine waters of the Galapagos Islands.
In fact, as we tick our wildlife checklist upon seeing several white-tipped sharks seemingly asleep on the sand some metres below in the rocky shallows off Bartolome Island, we are now on the lookout for hammerhead sharks.
Our guide, Tatiana Bucheli, knows exactly where each of the remote islands' animals and sealife are likely to be. Hammerheads are known to swim within the extinct volcanic caldera of Genovesa Island in the group's far north and the only island of the group in the northern hemisphere.
And sure enough, as if on cue, we follow our knowledgeable leader and within minutes are privy to a school of perhaps 10 huge hammerheads swimming by just metres below us.
"Sharks come out to eat only in the early morning and late afternoon," says Tatiana, who has worked as a naturalist guide in the Galapagos for 10 years. "There are 33 species of shark here out of almost 500 in the world," she adds.
But sharks are only one species of myriad land and aquatic animals that appear not to notice us.
Having lived with no known predators - particularly humans, for nearly all their lives, giant tortoises, metre-long land iguanas, spiny unattractive marine iguanas and all manner of exotic birdlife such as frigate birds, red-footed and blue-footed boobies have no fear and go about their business in these blissful isles totally ignoring the daily visitors.
It's a 90-minute flight from Guayaquil on mainland Ecuador 1000 kilometres away to the simple airstrip on Baltra Island. On arrival, most visitors are surprised, as Charles Darwin was 180 years ago, to find that even though straddling the equator, it is not hot at all.
We are welcomed on board the newest vessel to cruise the islands, the catamaran Athala II. Following a major fit-out last year, it was relaunched in October to cater for just 16 guests in eight cabins. There are two passenger decks, four cabins on each - those on the main level having small furnished private balconies - ideal for quiet moments and to enjoy spectacular sunsets and dramatic skies.
The main level also houses a spacious dining room at the rear where buffet meals are presented with a comfortable forward lounge-cum-library with pull-down cinema screen where briefings are held each evening before dinner. The upper level has a covered bar with extensive cushioned seating and tables and chairs for alfresco dining, reading or just chilling out over a refreshing drink. The rooftop solarium sports recliner deck chairs, a few fitness machines and a relaxing Jacuzzi - perfect for stargazing at night.
There are usually a couple of excursions each day with snorkelling, kayaking, swimming or sunbathing constant activities.
Smart passengers bring underwater cameras to capture coloured fish, sharks and spiny marine iguanas that seem to float spookily on the water's surface as they swim. Waters here are aquamarine and as clear as the local Pisco brandy.
Often described as a natural laboratory of evolution, these far-flung Ecuadorian islands became known after the English naturalist Charles Darwin spent five weeks here in 1835, his findings being the basis of his controversial book On the Origin of Species relating to evolution and natural selection.
By discovering how various wildlife and birds - finches and mockingbirds in particular - had evolved to their particular environments, Darwin alerted the rest of the world to the fact that these volcanic islands are unique. Being strong swimmers and good fliers, the unusual animal and bird mix is believed to have arrived here with the help of currents and prevailing winds from all corners of the world.
Today, rare and endemic wildlife include the lovable Galapagos tortoise, the waved albatross, the ubiquitous marine iguana, the brown pelican, the Galapagos penguin, Galapagos hawk, and Darwin's finches and while the flightless cormorant has "lost the ability to fly, they can dive very deep, using their webbed feet like a propeller", says Tatiana. "They can go down to 60 metres looking for octopus and eels."
There are 19 islands in the archipelago spread out over 45,000 square kilometres. Five are inhabited, the largest community being in Puerta Aroya on Santa Cruz where the Charles Darwin Research Centre is located. Most locals have made the move here to service the burgeoning tourist industry.
Declared a Unesco World Heritage Site, in 1978, along with Ecuador's capital, Quito, the Galapagos Islands were added to Unesco's List of World Heritage in Danger in 2007. They were removed from the danger list in 2010. Today visitors are capped at 140,000 a year with excursions to the same location restricted to once in 15 days.
Each island seems to have become the natural habitat to a particular species of wildlife: sea lions thrive on Mosquera Island, Galapagos tortoises and large land iguanas love life on Isabela Island, red-footed boobies and frigate birds abound on Genovesa Island, nearly the entire world's population of waved albatross live on Espanola, flightless cormorants and marine iguanas among others inhabit Fernandina Island (one of the most pristine ecosystems in the world and the youngest island).
Highlights of any holiday here are many: swimming among some 60 to 70 sea turtles, joining penguins as they dive and cavort, walking among nesting red-footed boobies, watching blue-footed boobies "sky-pointing" with their beaks as they dance on one foot then the other in courtship, being privy to the male frigate birds as they puff up their red neck pouches to attract females, seeing an elusive spotted sunfish which at several metres long is "the biggest bony fish in the world", according to Tatiana, and crossing the Equator when the GPS reads 0deg, 0deg, 0deg.
But the absolute highlight has to be swimming with playful sea lions that spiral around us, putting their happy whiskered faces to our masks for a closer look - almost begging us to show our skills.
Created over millennia by a series of volcanic eruptions, the islands are a mix of rugged landscapes, low-growing bushes, sandy beaches and extraordinary lava flows - all with masses of wildlife. On most islands, there are few shade trees and no structures or signs of human intervention or presence.
As Paul D Stewart says in his book Galapagos - the islands that changed the world, "the Galapagos fauna and flora remain a spectacular reminder of a planet before people".
Editor's note: The word Galapagos is derived from old Spanish Galapago, the frontal piece of a riding saddle, a shape similar to the shells of giant tortoises on the Galapagos Islands.
Tricia Welsh was a guest of Abercrombie & Kent and was assisted by Qantas Airways.
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