So how did you pass your summer vacation? A month at the beach? Vegging out at a summer cottage in Maine? Visiting your children and grandchildren?

Then there's Carolina Meadows resident Charles Kinnaird. Since retiring as a college and high school lecturer in humanities, he and his wife, Peggy, have spent many happy weeks as the guests of luxury cruise liners, touring the Caribbean, the Baltic, Mediterranean, and some of the more remote corners of the world.

The price of admission? Kinnaird's services as a lecturer to other travelers on the cruise ships.

When Kinnaird retired from his last teaching position as a humanities lecturer at a New Jersey High School in 1996, he had amassed considerable experience leading student tours through Europe. The first group of tourists that he led in 1962 consisted of 33 high school and college students and teachers, all female. One of the teachers was, like Kinnaird, a West Virginian and a West Virginia University grad.

"She was Peggy Brown, who was to be Mrs. Kinnaird," he said.

"I worked for a company in Minneapolis called American Youth Abroad," he said. Its function was to organize summer tours for students. As his summer tours continued, Kinnaird expanded his own knowledge with a sabbatical year of medieval studies at Oxford University, a summer of museum-going in Paris and a month at an archaeological dig in Israel. He took an unforgettable course in the art of the southern Renaissance taught in English at Scuola Lorenzo de Medici in Florence. All can be lumped as humanities, "which is multinational and covers the full sweep of mankind."

For both his summer tours and his winter job as a teacher, he accumulated a library of 35-mm slides to illustrate his lectures.

After retiring, he said, "I said to Peg, 'I would like to be a humanities lecturer on cruise ships.' She said, 'It sounds good to me. Take me along.'"

He sent letters and resumes to five cruise lines, not one of which responded. Then he met a woman who coached bridge players on cruise ships. He should get an agent, she advised, providing him with the name and address of her own agent. Soon afterward, Kinnaird received a call from the office of the agent: Would he be interested in signing aboard a ship of the Italian Costa cruise lines for a 16-day voyage from Miami to Genoa, Italy? The lectures should emphasize, though not exclusively, Italian culture.

"That is what I do," he responded.

A new career was launched. It was a career in an expanding industry, as the cruise lines were launching dozens of new ships, for millions of passengers, bound for destinations that most literally spanned the globe.

In 43 cruises he has taken in the past 10 years, Kinnaird has developed dozens of topics for lectures. Destination lectures inform the passengers about the ports they are about to visit; others known as "enrichment lectures" can be, as Kinnaird put it, "whatever floats your boat."

For a cruise along the Mexican Atlantic coast, he can talk about the Mayan ruins of Chichen Itza in the Mexican state of Yucatan; for the Caribbean, the explorations of Christopher Columbus and the geology of islands. The Mediterranean offers countless opportunities for discussions of Egyptian culture, Greek civilization, the origins of written language in Mesopotamia (better known today as Iraq), the art of the southern Renaissance, Roman culture and how it spread through Europe, and, almost everywhere, the art of the region.

A lecture on the First Crusade (1095-1099) is especially relevant today, as the Crusades, nominally to regain the Holy Land for Christianity, are still a source of anger among Muslims.

Midway on a cruise from Valparaiso, Chile, around the southern tip of South America, from a stop in Ushuaia, Argentina, Kinnaird and his wife boarded a charter aircraft for a flight over Antarctica. By the sheerest coincidence, they were eyewitnesses from the air as a huge island of ice broke away from the continent. This suggested lectures on a topic that has since entered the language, global warming.

The life of a shipboard lecturer is not unduly rigorous, Kinnaird has found. No lectures are scheduled on days when the ship is in port and the passengers are ashore. Typically, on a 12-day cruise, he will give five to seven lectures, each on a different, self-contained subject, and carefully timed at 45 minutes. The ship provides a technician to operate a Power Point presentation. The audiences sometimes are large enough to fill a ship's auditorium.

Afterward, the speaker is recognizable to passengers, who treat him as a celebrity and like to engage him in conversation. For shore excursions, the lecturers may volunteer to assist the ship's staff to escort the passengers and listen to the local lecturers engaged to inform and entertain the passengers.

This year, the Kinnairds are looking forward to yet another cruise, this one in September aboard Royal Caribbean's Legend of the Seas for 12 days, beginning and ending in Rome. One of the stops will be Dubrovnik, Croatia, a spot that he has somehow missed in his previous travels, and another the port city of Split. Even for the well-traveled, there are always new frontiers to explore.