When a First-Timer’s Luxury Cruise Turns Into an SOS

IT’S A MYSTERIOUS TRUTH I’ve yet to fathom, but the fact is that a stranger’s opinion, delivered forcefully, often carries more weight with me than it should. The stranger in question was a man of a certain age, holding forth at a cocktail party in London on the pleasures of a world cruise.

I was about to write a novel in which a character sails from Europe to Africa in the early years of the 20th century. My study was full of images of the great liners—Titanic, Aquitania, the Kaiser Wilhelm der Grosse. These ships, in first...