During the January trip, Barbados guide Victor Cooke makes a point at a marker explaining future president George Washington's seven-week stay - at 19 - which may have altered U.S. history. Picture: Linda Nelson Nash for The Washington Post.

We were three couples who wanted to know how the histories of the United States and the island intertwine, and we discovered — on that pocket of sand and elsewhere — that tailoring your own onshore excursions can give you a far more interesting and sometimes less expensive vacation than your cruise line's prepackaged offerings.

Our guide was Lennox Honychurch, the author of several books on the island's history. He also happened to be press secretary to the prime minister of Dominica back then, when local renegades plotted with some violent Rastafarians — "the Dreads" — and a seagoing North American racist cabal.

But the captain of the boat they hired to bring them over told federal agents instead, Honychurch told us. "So they were all arrested when they got to the dock in New Orleans, and their mercenary adventure was cut off." All but forgotten, it was one of many strands that bind our two histories. And we wouldn't have known about it if we hadn't gone off book.

It's easy to customise your shore excursions, even on the well-trodden Caribbean circuit, which accounts (with the Bahamas) for about 35 percent of world cruise passengers. A few weeks before you leave, pick any theme that spikes your curiosity. Line up some modest background reading to share, then contact local guides.

You'll benefit local people more directly, too - a small boost for hurricane-hit economies like the ones in Puerto Rico, St. Croix and Dominica, which were among the six ports of call we explored on our seven-day cruise. Locals told us that when you book excursions through the cruise lines, they scoop up as much as 40 percent of the money on the table.

At San Juan, our friends Ken and Cicely studied up on Puerto Rico's historical embrace of the United States, at times warm but often frosty. 

They explained at dinner the evening before our tour that the island's government is only partly independent of our own, as our guide, the gregarious and brainy Carlos Medina, affirmed the next day. 

He was especially well qualified to lay out the economic details of this relationship for us. "I worked for Merrill Lynch's institutional branch for 22 years!" he told us.

Puerto Ricans are U.S. citizens, but they cannot vote for president and they don't have congressional representation — but they pay no federal income taxes.

 Their two biggest political parties advocate either a push for statehood or maintaining the status quo. We mulled all that over with Carlos, who was delighted to jump the tracks and depart from more typical tourist banter. 

These conversations came instantly to mind when, months later, two hurricanes brought devastation and the U.S. relationship with Puerto Rico was a focal point.

The reading prep also allowed us to discover that 2017 is the centenary of the U.S. purchase of St. Croix and the other U.S. Virgin Islands from Denmark for $25 million. (No mention of this in the cruise-ship bulletins, where you could learn instead about getting a seaweed massage, or how to join a "Rolex competition." Those may appeal, but they can just as easily take place in a mall somewhere.)

Across a steep ravine overgrown by a tropical jungle, we took a careful walk along the high and slender edge of the derelict Creque Dam in St. Croix.

It created a water supply for the town of Fredericksted, built by U.S. Navy engineers during the 1920s, when they administered the territory just after the takeover.

It was safe to guess that ours was the only table at dinner onboard that night where the Great War, nation-building and the question of what might be done to help St. Croix, our American territorial ward, were closely examined.

In preparation for the next port of call, our friends Jim and Laura poured a glass of wine and told us what they'd gleaned from their readings on the surprising cultural kinship of Bridgetown, Barbados and Charleston, South Carolina.

Our guide there, Victor Cooke, walked us through that history the following day. Many Barbadian slave owners immigrated to the Carolinas and founded Charleston in 1670. An estimated 7 million Americans can claim Barbadian lineage. At 19, George Washington spent seven weeks here — the only visit he ever made outside the United States. We learned during a tour of the house where he stayed — now a fine museum in Bridgetown — that he contracted smallpox and developed an immunity that saved him, a quarter-century later, when many of his troops died of the disease during the Revolutionary War. What if we'd lost Washington to smallpox then?

Grenada, our final landfall, was the target of a U.S. invasion in 1983 to fend off a Marxist coup. The opinion that the United States should not have intervened in the destiny of another sovereign nation was shared by many of our enemies and allies.

But the invasion was not unpopular in the United States, and had the firm support of both Dominica and Barbados, which were eager for stability and safety in their own democracies. Our guide Mandoo Seales showed us sites connected with the 11-day invasion, which he lived through. Nineteen American military personnel were killed.

Cicely summed it all up on our last evening. Grenada, she said, is beautiful and engaging. And also, behind the airbrushed presentations offered most visitors, it is a place of pathos.

Planning these explorations wasn't hard. They lifted our cruise well out of the predictable and often saved us money, too. There was still time, let me add, for a contrapuntal round of cruise-ship bingo, trivia contests or that seaweed massage.

Source: The Washington Post.