Embarking on one of the world’s great expeditions into a world full of wildlife and wonder.

By Antonia van der Meer

It is my fifth day aboard the luxury Silver Galapagos expedition ship, the newest addition to the Silversea line, and my transformation is almost complete. As I swim through the waters of Champion Island, well insulated and buoyant in my wetsuit, I believe I am becoming part sea lion. Snorkeling once or twice a day, I am on the hunt as they are, chasing penguins and colorful fish.

My ears stick out slightly, pushed down by the tight strap of my mask. (External ear flaps are one of the most obvious ways to distinguish a sea lion from a seal.) Suddenly, a pod of sea lions greets me as its own, swimming toward me and peering straight into my eyes, then bending and twisting as they spiral down below me, only to pop back up by my side. What I do, they mimic: a twirl, a splash, a dive. I watch as one playfully picks up a starfish in its mouth and starts a game of sea lion Frisbee for which I now have a front-row seat.

I am on an expedition, and an expedition is nothing like a cruise. Evidence: The ship has four lounge chairs on board for its 100 passengers. More evidence: They're always empty because no one has the time (or desire) to lounge. Expeditions, on land and in the water, head out twice a day; some start as early as 6:30 a.m. The cabins are spacious, and most have small decks, but we are kept so busy that all we really see is the bed when we crash there immediately after dinner.

We are sped in expertly manned Zodiacs to otherwise inaccessible landings of interest throughout the archipelago. And from these posts, we are able to see the most wondrous things: the striking contrast of a tiny yellow warbler perched on the mottled shell of a giant tortoise; the bulletlike speed of penguins darting through the water after a school of fish; a dark, craggy cliff against the outrageously turquoise feet of a blue-footed booby unaware of its own impossible beauty; the heartbreaking cries of an orphaned baby sea lion as he seeks solace from other mothers, only to be rebuffed by angry barks. (Helping him might endanger their own lives and offspring.)

The Galápagos Islands (named after the Spanish word for a type of saddle, used to describe the now-endangered giant tortoises) are famous for inspiring Darwin's theories of evolution. He spent five weeks here; I only have one in which to see the abundant wildlife: finches, sea turtles, pink flamingos, marine iguanas, and bright red crabs. One of the most amazing things is that they are unafraid of humans. They don't even blink when we lean in with our protruding lenses.

The islands themselves are less photogenic: most are inhospitable piles of lava rocks, leftover from fiery active volcanoes. Some islands look like drip castles; others, like vast landscapes of dark chocolate butter-cream whipped by electric beaters. It's a place where very little grows, and there is almost no freshwater.

Putting it in context for us is a wonderful team of Ecuadorian naturalists, certified by the national park. They are our onboard guides as we travel 435 nautical miles through this place of complete otherness smack dab on the Equator. But thanks to them (and the sea lions), I find myself strangely at home in a world I once barely even knew existed. —Antonia van der Meer

Rates for a seven-day cruise on the Silver Galapagos start at $5,850 per person; silversea.com.

Photos, from top: Frans Lanting/National Geographic; Todd Mintz/Alamy; Danita Delimont/Getty Images