TRAVEL UPGRADES are usually nice, like a Creamsicle at the gates of hell, but as we discover with Horizon Yacht Charters, they can also totally save your hide. A previous charterer ran the monohull we'd reserved onto a reef, so owner Jacqui has upgraded us to a lavish 38-foot catamaran, with something that Sam has never seen in his 30 years of sailing: two refrigerators! We stack away the 87 pounds of bars like so much gold bullion, snugly filling both fridges, as if they'd come with stickers: PERFECTLY FITS 348 4-OZ CHOCOLATE BARS.

I place the probe of my chicken-roasting thermometer in one of the fridges. This connects to a digital display I've mounted beside the cockpit instruments. "Sixty degrees and holding!" I yell to Sam, who's cracking a beer.

We motor-sail 30 miles into the wind to sleepy Tyrell Bay, on the island of Carriacou.

Our plan is salty simple: The first two days we'll sail north 80 miles to the island of Bequia, then zigzag back through the sprinkle of islands between Bequia and Grenada, selling chocolate in towns as big as a couple thousand and on isolated palm planters with no more than a fisherman's shack. In between, we'll enjoy some glory sailing, the 15-knot winds blowing out of the east allowing us to hot-rod south, the boat knifing through the swell, cockpit fully shaded by the awning, few if any other white triangles in sight.

We hit terra firma feeling—and looking—good. We carry a soft-sided, Windex-blue briefcase cooler from home and wear matching T-shirts emblazoned with the colorful GCC logo, which Mott's distributor in New York, a dreadlocked Italian Rasta nicknamed Pastrami, helped us create.

Our semi-legit appearances notwithstanding, our reception at La 'Qua Supermarket is less than enthusiastic. Miss Diana, the large owner of the dimly lit store, wants only milk chocolate.

I pull out a sample bar and let her admire the hand-drawn label of plump cocoa pods before peeling it back to reveal the rapidly melting bar itself. She chews slowly.

"What da deal you do?" she asks.

I tell her our prices as a gaggle of older men draped on a picnic table pass the sample around. Then she produces an Oh Henry! and rattles through a lot of quick, complicated math to show that our dark chocolate—blech—is far more expensive per ounce than her nougaty, milky-yummy Oh Henry!

Sam turns to an old man sampling away: "What do you think?"

"Is pure, good for da heart," he says, waving the sample at Miss Diana.

She shakes her head in mock disgust, as if to say You can always count on the stupidity of men, and buys a dozen.

Ka-ching!

Throughout the day, Sam and I perfect our hokey good-cop/bad-cop routine—I talk money, Sam gushes sweetness—and the women store owners continue to put us through the wringer, my favorite being Miss Phyllis: "Dis a sample? I don't like chocolate." But really, on Carriacou, the chocolate sells itself. Miss Phyllis buys seven dozen.