On the southwest coast of St. Lucia, the mountains sheltering Soufrière Bay rise from far below the surface of the water, so the harbor is precipitous and deep, encouraging even large yachts like Emerald Seas to anchor so close to shore that we tossed a stern line to a pair of fishermen waiting in a skiff who ran 20 yards to the beach and tied it off to a tree. Afterwards Emerald Seas’ owners, Glen and Mary Lancaster, and their guests–a small group of charter brokers and I, chaperoned by LeAnne Morris Pliske and Anna Spurling of The Sacks Group–slipped one by one into the still, transparent water to loll between the stern and the shore. On the beach photographer Gary John Norman shot portraits of a pair of kids balanced partway up the trunk of a palm in the warm August evening. Above him the foliage on the steep slope hid a dirt road running from town to a cluster of nearby houses. You could hear the voices of locals passing homeward in small groups, and every few minutes the bushes behind Norman would rustle and another couple of curious children would emerge. Within 20 minutes he was at the center of a dozen gamboling youngsters. Those of us reclining in the cool water looked on with amusement.

This tableau unfolded in the shadow of the northernmost of a pair of natural wonders known as the Pitons–twin spike-shaped mountains rising spectacularly from sea level to more than 2,500 feet. In this embrace, our idyllic anchorage was charged with extra significance. Petit Piton loomed with the strangely inert drama of the monumental; it was as though we had come to rest beneath the Matterhorn or at the foot of a pyramid.

The Pitons are a breathtaking national treasure in a country just 27 miles long and 14 miles wide, but they are not the St. Lucians’ only pride. Soon after our arrival on the island the day before–once Glen Lancaster had met us at the airport, ushered us 15 minutes north to Emerald Seas at Rodney Bay Marina, and settled us in our staterooms–Norman and I jumped into a taxi for an improvised tour. During a two-hour drive that took us through the stop-and-go streets of the capital, Castries, and south along a switchback coastal mountain road as far as the fishing village of Anse La Raye at the island’s midsection, our driver Linus, a young, loquacious Castries native whose radio-taxi handle was "Intellect," guided our attention to a variety of sights conventionally worthy of a tourist’s interest. But he also gave weight to modest features of his tiny country that most visitors would likely disregard.

Thus at the center of Castries he noted that the square adjacent to the 1897 cathedral was named in honor of Derek Walcott, the St. Lucian poet who won a Nobel Prize in 1992. Yet a moment later his pride seemed just as strong as he pointed out the new engine at the capital’s central firehouse. Amid stunning views from Fort Charlotte atop Morne Fortuna, a 2,800-foot mountain overlooking the city, he told us that the 1796 citadel had been restored as a college named for yet another St. Lucian Nobel laureate, the economist Sir Arthur Lewis. Yet he beamed just as brightly when we passed St. Lucia’s humble TV station. "Just take a look at our dishes, man," he said of the cluster of sun-bleached antennae.

At first I took a patronizing view of Linus’ generous enthusiasms. But by the end of our drive I saw nothing naive in his patriotism. The size and assets of his island nation should not have governed his pride. It was as genuine as any Yankee’s, and as valid.

This was a valuable perspective as we explored St. Lucia’s west coast and a handful of islands in the Grenadines to the south. As a first-time visitor to the Caribbean, I welcomed any help in grasping its proportions. From afar, extraordinary symbols like the Pitons loom like illusions of paradise, and one postcard of an achingly perfect beach can epitomize–and somehow obscure–a dozen countries. But traveling by yacht with occasional forays to land, we were able to take measure of these island nations in relation to our wake–sometimes literally. Before we left Marigot Bay, another of St. Lucia’s coastal gems where we’d stopped for a while to play on quiet beaches and sip drinks at a local cafe, we entered its stunning, steeply sheltered inner harbor, where there was just enough room to spin Emerald Seas on her axis. We couldn’t have more graphically appreciated its dimensions.

When a floating home is so substantial, she takes on a culture of her own. Emerald Seas, with her rich mahogany interior set off by polished nickel brightwork, suggests an earlier age of cosmopolitan luxury. Myriam Tremblay, her French-Canadian chef, prepared superb meals of North American fare with global flair–for example, preceding herbed rack of lamb with tangy gazpacho perfect for the climate and accompanying it with roasted potatoes and juliennes of carrots and the Caribbean vegetable christophene. Our Trinidadian captain, Cyprian Vialva, oversaw the yacht’s operations with the dignified confidence of a 30-year professional, and his crew’s cordial demeanor seemed influenced both by the bucolic beauty of the island setting and a classic Southern graciousness imported by the Lancasters from their native North Carolina.

At 105 feet LOA Emerald Seas sometimes rivaled in size the Grenadine islands we visited. Bequia, a night’s run from St. Lucia, is the largest in the group, yet is only seven square miles in area. On the beaches of Admiralty Bay, encircled by its main town, Port Elizabeth, small brightly colored sailboats the locals have used for generations rested on their keels. Proportions on Bequia have taken a playful turn. Once a regional center for boatbuilding, the island is now best known for the finely detailed model ships made by patient masters such as the Sargeant brothers, whose workshop we discovered just a short walk from the crescent of small shops and relaxed restaurants along the waterfront.

Seven miles southeast of Bequia on privately owned Mustique, Britannia Bay harbors just one restaurant, the famous Basil’s Bar, which we found remarkably convivial, considering its select location. The likes of Mick Jagger and Tommy Hilfiger own homes on Mustique and help make it one of the most exclusive destinations in the Caribbean, so a 30-minute taxi ride past dozens of Edenic estates was in marked contrast to our jaunt with Linus on St. Lucia a few days before. Here our driver merely recited facts and figures for each mansion–the nationality of the owner, the baffling number of rooms, and the mortifying rental fee. Amid Mustique’s carefully manicured scenery, I missed Linus’ exuberance for a particularly fertile stand of banana trees or a fishing village’s dusty cricket pitch.

On a large yacht exclusivity travels with you. A few hours’ run south of Mustique, Vialva expertly negotiated a hair-raising labyrinth of reefs to reach the pocket-size refuge of Horseshoe Cove in the Tobago Cays. Once we were anchored, every guest took to the aquamarine waters by kayak, RIB, or just a pair of fins, and for a few hours the teeming reefs and deserted islands seemed like our private archipelago. Looking back on the yacht from the blinding-white beach on one of the cays, I realized that a charter on this level is sometimes a means of exploration, sometimes a retreat, but best of all, often both at once.

Later, as had become my habit after another of Tremblay’s exceptional dinners, I reclined in a long chair on the open aft deck. Distant lights on Carriacou and Union Island were visible on the horizon, but our anchorage was dark under late summer meteor showers. Five days of cruising had eclipsed and annulled the postcard image of the Caribbean I’d held before my arrival, and I no longer puzzled over its proportions. All I could do was wonder when last I’d seen such a densely starlit sky.