We swim with five Galápagos sea lions that buzz snorkellers underwater — they dive straight for me like fighter jets, then spin away at the last second, grinning.

Later we dive overboard to snorkel. 'Don’t worry,' Harry jokes, 'Galápagos sharks are vegetarian.' Or just well fed — the ocean teems with sea life and I see myriad tropical fish, one green turtle and four white-tipped reef sharks.

Darwin once called his voyage "one continual puke"

That was just snorkelling; the Galápagos is a superb scuba-diving destination, with sights including vast schools of eagle rays and dolphins, penguins, manta rays, Galápagos sharks, whales and whale sharks. The best dive sites are up north at Wolf and Darwin islands, where divers swim with hundreds of hammerheads, but these are not on a five-day itinerary.

Our next stop is Española Island and, like all major distances, this stretch is covered at night, so we wake up to a new island daily. The seas are rough so I can't lie back in a deckchair to admire the brilliant constellations; I empathise with Darwin, who suffered terribly from seasickness and once called his voyage 'one continual puke'.

The next day dawns calm and clear in Española’s Gardner Bay. Fur seals are strewn the length of the beach — some cuddling like young lovers, one seal with a flipper over the other. Marine iguanas crawl out of the ocean onto the rocks, where they crouch to dry off.

These are one of the unique attractions of the Galápagos, but the world’s only sea-going lizard did not at first impress Darwin, who described it as 'a hideous-looking creature', but which in the water swam 'with perfect ease and swiftness'. The land iguanas fared no better: 'Like their brothers the sea-kind, they are ugly animals ... [with] a singularly stupid appearance.' And they weren’t even tasty: 'These lizards, when cooked, yield a white meat, which is liked by those whose stomachs soar above all prejudices.'

We're not alone in Gardner Bay — also anchored here are three big cruise ships. Despite the Ecuadorian government monitoring visitor numbers to protect the marine park, Harry, who’s been guiding for over 10 years, says the number of licensed boats plying the route is increasing. He shrugs: 'Money buys everything.'

Five days pass quickly, partly because the fifth day ends at 10am, when we’re returned to the airport. And the amiable Texans were right: only once did we get the sails out — and that was to provide shade on the main deck. There's just enough time for a sunrise walk before check-in. We’ve seen scores of birds, including the endemic lava gull, Galápagos dove and a pair of albatrosses that performed a mating dance, then did the deed in front of us. Today, we’re expecting frigate birds.

The air is scorching by 8am and while I'm never thirsty enough to kill a tortoise to drink the water in its bladder, as Darwin reports inhabitants did, I drain bottles of water on even short excursions. We stroll past sea lions snoozing under shady bushes (‘More seals,’

I hear an American woman disinterestedly confide to her video camera) and find the male great frigate birds in full courtship mode. They’re great big black birds with a red chest pouch that inflates like a balloon, seemingly to the point of bursting, possibly with male pride. Apparently, girls love it. I do. No wonder early explorers called the Galápagos Las Islas Encantadas — the Enchanted Isles. There’s magic in the air.

Travel notes:
• BEST TIME TO GO: May is a good month as it’s breeding time for birds and before high tourist season (June to August). The climate is subtropical, with a hot rainy season (January to April) and cooler dry season (June to November). Animals are seen year round.
• CURRENCY: US dollar. $1 = about R9,15. Notes are identical to American money, but coins feature famous Ecuadorians, not the US presidents.
• VISAS: South Africans do not require a tourist visa to visit Ecuador or the Galápagos.
• HEALTH: Immunisations are not required for the Galápagos, but are a must for mainland Ecuador; consult a doctor for the current list. Drink only bottled water.
• WHAT TO DO: It’s possible to take independent ferry trips to some islands (just not the ones with the most wildlife), but the best way to see the Galápagos is on a licensed organised cruise, usually five or eight days. Be aware that 'five' days is often three days, with a half-day taken up with arrival and departure business tacked on either side. Boats sail similar routes: bigger luxury catamarans have the advantage of being faster than little yachts, but more people on board makes for cumbersome land excursions.

  Nonprofit tour-operators group IGTOA (igtoa.org) is a good resource for tour information. I can recommend Columbus Travel (galapagosisland.net), which offers everything from budget five-day sailing trips for $900/about R8250 to eight days on a luxury cruise ship for $4000/about R36 650. It’s worth spending a day on the main island of Santa Cruz to explore around the town of Puerto Ayora. Most cruises depart from here and the Charles Darwin Research Station is within walking distance. Find news of Lonesome George and other conservation issues at the Galápagos Conservancy (galapagos.org).

• NEED TO KNOW: The Galápagos archipelago was declared a national park in 1959, 100 years after The Origin of Species was published. A $100/R920 entry fee is paid on arrival (galapagospark.org). Spanish is the official language, but most guides speak English.
• READ THIS: The Origin of Species by Charles Darwin (Gramercy) and The Voyage of the Beagle: Charles Darwin’s Journal of Researches (Penguin Classics).
• GETTING THERE: Local airlines TAME and Aerogal fly from Quito, the capital of Ecuador, to the Galápagos Islands. British Airways flies to numerous destinations in South America from London and Madrid. ba.com