This is the second dispatch from the 94-foot Trinity/Halter expedition yacht Whale Song as she completes a circumnavigation. The writer and photographer, Tom Zydler, is her captain. Grant Wilson is her owner.

After exploring Antarctic ice and the Chilean channels, the 94-foot Trinity/Halter expedition yacht Whale Song headed for the Galápagos Islands. All the way from Peru, the voyage felt like an effortless glide. Aided by following winds and the cold Humboldt Current, we throttled down the Caterpillars, boosted our fuel efficiency by 30 percent, and still made 240 nautical miles a day. The engines hummed, barely audible, and the yacht’s owner, Grant Wilson, remarked about our eerily smooth passage.

The course cut northwest over glassy swells, now and then broken by swirls of boiling water—teams of tuna feeding on frenzied anchovetas. Busy schools of beak-nosed dolphins swam by. A few lazy whales wallowed afar. Three hundred miles from the Galápagos, the midnight watch reported strange clicking sounds. I stepped out on the bridge wing and the ghostly outline of a bird flashed by. The echo-locating, nocturnal swallowtail gulls from the Galápagos found squid in the glare of our lights.

One reason we selected the Galápagos Islands for a stopover was that the owner and his family, including all of his grandchildren, would be joining my wife Nancy and me and our crew on board. They all wanted to experience this slice of Eden on earth.

The Humboldt Current, our conveyor belt, tends to upswell against obstacles like islands. Colder water loaded with plankton plumes to the surface, providing a feast for birds and fish. Near Isla Española, the water plunged to 71 degrees Fahrenheit, drawing thick flocks of petrel seabirds. Rafts of waved albatross gathered on Punta Suárez and just beneath its cliffs. It was April, the birds’ time to see their lifelong mates again after six months’ separation spent roaming the oceans. Almost all of this species, some 12,000 pairs, breed only on Española.

Before laying eggs, the albatross couples reinforce their bonds in an awe-inspiring ritual. After a moose-like call, they yawn and gurgle, then whack their beaks (which are the size of sword scabbards) a few times, gurgle again, then bow forward and sideways, repeating this routine again and again. We were able to watch them from a few feet away since Galápagos animals still don’t fear humans.

Puerto Ayora, the business center of the island chain, was booming. During a visit in 1986, we had chicken soup for lunch under a thatch roof on the dirt road overlooking Academy Bay. Today, visitors might need reservations to get into restaurants on the paved waterfront.

Continuing onward, three sea lions looked at me reproachfully for disrupting their sleep on our swim platform. Bands of brown noddies perched on yachts to spot fish. Marine iguanas swam by. Wild tortoises plodded through the hills above Puerto Ayora. Fond of ripe fruit, they slumber under the mango trees. On Rancho Primicias, an observant giant made straight for two-year-old Amelie’s bright yellow Crocs.

Isla Santa Fé, a two-hour steam away, hosts a sea lion nursery. On the island, sea lion tots stared at us intently, torn between fear and a desire to touch. The kids had to goose-step over marine iguanas sprawled on paths digesting wads of algae. A diving pelican came up with a large pargo (snapper), and two others dove on him as he tried to align it down his beak. The three snatched and tossed the fish until one succeeded in swallowing it. A blue-footed booby watched the scene disdainfully, preferring to feed by aerial bombardment—kamikaze plunges onto shoals of baitfish called salema. Near the sandy beach, a baby male sea lion, lithe as a flamenco dancer, played with a handkerchief that had fallen from a tour boat.

Our next anchorage, between Isla Lobos and Isla San Cristóbal, sounded like old MacDonald’s farm with sea lions bleating and retching all night. At dark, our underwater lights came on, drawing in small wiggly things. A large sea lioness lurking under the hull gulped yellow-banded eels like candy.

The computer-tweaked itinerary sent Whale Song eastward to Santa Fé and San Cristóbal, followed by Española and Floreana. Next was the grandest of all: the 70-mile-long Isla Isabela. Cold waters along her western shores support most of the Galápagos’ animal life. Here, right on the equator, penguins survive, as well as tropical flamingos. Not only does Isabela host most of the animal life, but it also looks dramatic. In contrast to the older, eroded islands we’d visited, six volcanoes rise into Isabela’s skyline, with another big one (at 4,500 feet) on Isla Fernandina, practically in her lap.

Isabela also has our guide Antonio’s favorite haunts, and he shared them with us. In Elizabeth Bay, we snorkeled through an inlet cutting into fields of lava frozen into razor sharp cones. Few visitors come here, and a sea lion pup—teddy brown against jet-black lava—watched us with obvious disbelief, frequently dipping under the water as if to clear its head. Tiny bubbles gleamed on the underwater rocks, venting pent-up pressure from the netherworld.

Isabela carries the region’s most aggressive volcanoes. Sierra Negra erupted in 2005. Floating over rosettes of algal plants, we nearly collided with several Pacific green turtles. Disturbed from their slumbers, they raced out—big, dark shapes oddly out of focus in the cold, mirage-like mix of seawater and freshwater.

On the nearby Marielas islets, Galápagos penguins—midgets compared with their Antarctic cousins—share the sea with flightless cormorants that viewed our intrusion through strikingly blue eyes. Inland, in mangrove-bordered lagoons, lazy turtles slept on the mud bottom. Dozing sea lions stretched on fallen trunks.

Isabela continued to deliver thrilling surprises wherever we anchored. In Tagus Cove, the crew of visiting ships used to paint their names on the surrounding cliffs. Still clearly readable, Hussar 1932 was as moving as it was unexpected. Grant’s grandfather was then the skipper of the grand yacht, later named Sea Cloud when Marjorie Merriweather Post divorced E.F. Hutton and became the sole owner.Volcán Ecuador marks the northwest tip of Isabela. Though only 2,000 feet high, the sheer vertical wall of red rock rises dramatically over the anchorage at Cabo Vicente Roca. Here, the equator is very close. Come daylight, Whale Song steamed northward, passing two enormous fish heads belonging to the sunfish that frequent the area. We stopped at zero degrees latitude. All five kids, Margaux, Amelie, Tripp, Ike and Bob, stepped over "the line" (an old rope strung across the bow) and suffered cold seawater poured over their heads while chanting, "I love the motion of the ocean." It was an easy equatorial baptism in view of their ages.

Our guide had another favorite place on the east side of Isabela. Off Cabo Marshall, Antonio led our divers through clouds of silvery salema and straight into a cloud of hammerhead sharks. Overhead, manta rays winged their way along disdainfully, black clouds against the shimmer of the ocean’s underside.

Seabirds own Isla Genovesa. More than 140,000 red-footed boobies roost there, and the trail around the sandy beach near the anchorage offers an in-your-face show of Nazca and blue-footed boobies, frigate birds, swallowtail gulls, lava herons and finches. The afternoon breeze brought shearwaters racing in looping sweeps by the steep cliffs. Frigate birds, lacking glands to waterproof their feathers, crowded the sky and fed themselves by robbery, tormenting the birds returning from fishing. One yanked the long tail of a tropic bird, catching its regurgitated lunch in mid-air. Screams of ravaged birds echoed off the bluffs.

Four tour boats crowded the anchoring shelf in the abysmally deep Darwin Bay. They left with their tourists late in the day, which is the coolest time to venture to the plateau. There, palo santo (holy wood) trees and thorny bushes cover the eroded terrain like wisps of thinning hair on a bleached skull. Clearly, the birds liked it. Over the windward shore, swarms of storm petrels fluttered like butterflies. In the scant shade of bushes, boobies tended large fluffy chicks. Under the cliff overhangs, fur seals were waking up, and young males tried their strength in mock fights.

Old whaling-ship sailors called the archipelago "Islas Encantadas" (the bewitched or enchanted islands), referring to the variable currents and sudden fogs. Yet the nickname fits these GPS days, too. The volcanic islands are riding southeast on a tectonic plate at nearly two inches a year. The geologically young Isla Santiago and nearby Isla Bartolomé have the texture and color of a cooling inferno. Santiago’s red slag heaps glow against blankets of black, ropy lava like wrecks from the big bang. On Bartolomé, we walked on the shoulders of a dead volcano above gaping spatter cones of jagged cinder. The landmark Pinnacle Rock leans over the anchorage like a finger warning of the earth’s frailty, yet on life goes. Later that night, we shut off the underwater lights to keep misguided turtle hatchlings from bumping into the swim platform.

Every voyage through the Galápagos Islands makes me long for another. Is it because in other places animals and land vanish, rapidly displaced by development for human needs? I wonder how long the Galápagos will survive? Considering the instability of Ecuadorian politics, let’s hope Kurt Vonnegut was a joker and not a prophet when he wrote "Galápagos" in the 1980s.