Also, would civilians in this time of history sailing for pleasure fly their country's flags like modern sailboats do today? such as this?
Some Example situations
War of Spanish Succession: I'm a Spanish citizen on the northern coast of Spain, I go fishing for a living and for sport. I decide to take my small boat out to the open sea, I sail pretty far North, north enough until I see a British man o' war. Oh no! It's scary! What do I do? Will I sail back to the coast as fast as I can, or will the British Man o' war think the little fishing boat has a spy on it? Or do I just stay in the same spot to hope it just sails away?
American Revolution (1776): I'm a peaceful American-born citizen living in Virginia (in what would now be modern-day Norfolk), and I can see the Chesapeake Bay from my house. I want to visit my cousins who live in Delaware. I could go around the entire Chesepeake Bay on land by horse, but it would take too long. So I decide to use my sloop, or schooner (or whatever I have) to sail from where I live to Delaware. Halfway across the trip, I see British warships escorting a British merchant navy ship, there is a frigate, 2 brigs, and 3 sloops-of-war. I want to continue my way but I'm scared, as I heavily support the Patriot cause. What could happen in this situation? How would they react?
Napoleonic Wars: I'm a very rich citizen from London, England. I decided to host a party on a brig I recently bought (for pleasure sailing purposes, no cannons on it). I sail out with my friends. I may or may not be sailing the English flag (Idk, would I?). I sail out pretty far East, it's a nice, sunny, cloudless day and all of a sudden I see a big ass fleet of French warships ; 3 ships of the line, 2 man o' wars, and 4 heavy frigates. My friends and I start freaking out. My brig is fairly big in size and could easily be seen by these warships from their point of view of the horizon. They see that my ship has sailed this far (so automatically, they would know I sailed from England, right?). What would they do? seeing that my ship is pretty big, plus I'm a rich citizen (not affiliated with the navy), only rich people could own a boat of this size, right? Would they try to take my ship for any prizes onboard? Or would they just leave me alone?
Golden Age of Piracy: I'm a fisherman on a small boat sailing across the Bahamas to a specific destination, as I desperately sail from the pursuing Pirate brig that's gaining on me (but well out of range), I see a British (or Spanish) frigate patrolling these islands, do I sail near the ship in hopes that it sees the Pirate brig chasing me, and eventually open fire on the Pirates? Would it be more hostile to the Pirates than my puny little boat?
4. On the whole, pirates tried to avoid getting entangled with naval vessels, especially something large like a frigate, so for you to hang around with one would give you a fair level of immunity from pirates. However, depending on your own nationality you might want to think twice about going near a frigate. The British in the Caribbean tended not to bother stopping small vessels like your fishing boat, but the Spanish were a different matter. The Spanish naval presence in the Caribbean was fairly limited most of the time, but they relied heavily on Guarda Costas, privateers with coast guard duties, who were noted for their unscrupulousness in picking up trading vessels of other nations and imprisoning their crews.
Pertinent only to the sub-question, and really the very tail-end of the Age of Sail, but Joshua Slocum wrote about his solo circumnavigation in Sailing Alone Around the World, which is more or less a pleasure trip (he does work during the voyage, but it's more of the raise-funds-keep-sailing kind of job).
His voyage takes place in 1898, and he has a section - it's online here - where he talks about the Spanish-American War breaking out, and a moment of panic when he's afraid his flags on Spray might be spotted by a Spanish ship off the coast of Brazil, near what's now French Guiana.
I did not know that war with Spain had been declared, and that I might be liable, right there, to meet the enemy and be captured. Many had told me at Cape Town that, in their opinion, war was inevitable, and they said: "The Spaniard will get you! The Spaniard will get you!" To all this I could only say that, even so, he would not get much. Even in the fever-heat over the disaster to the Maine I did not think there would be war; but I am no politician. Indeed, I had hardly given the matter a serious thought when, on the 14th of May, just north of the equator, and near the longitude of the river Amazon, I saw first a mast, with the Stars and Stripes floating from it, rising astern as if poked up out of the sea, and then rapidly appearing on the horizon, like a citadel, the Oregon! As she came near I saw that the great ship was flying the signals "C B T," which read, "Are there any men-of-war about? " Right under these flags, and larger than the Spray's mainsail, so it appeared, was the yellowest Spanish flag I ever saw. It gave me a nightmare some time after when I reflected on it in my dreams.
I did not make out the Oregon's signals till she passed ahead, where I could read them better, for she was two miles away, and I had no binoculars. When I had read her flags I hoisted the signal "No," for I had not seen any Spanish men-of-war; I had not been looking for any. My final signal, "Let us keep together for mutual protection," Captain Clark did not seem to regard as necessary. Perhaps my small flags were not made out; anyhow, the Oregon steamed on with a rush, looking for Spanish men-of-war, as I learned afterward. The Oregon's great flag was dipped beautifully three times to the Spray's lowered flag as she passed on. Both had crossed the line only a few hours before. I pondered long that night over the probability of a war risk now coming upon the Spray after she had cleared all, or nearly all, the dangers of the sea, but finally a strong hope mastered my fears.
Earlier, Slocum receives a gift of a new flag while passing through... I think it's the South Pacific, or perhaps northern Australia... and is glad to be able to fly it.
Within his narrative, it seems a little like good etiquette to fly one's colors, almost like an introduction you'd make to another ship's captain or the harbormasters on shore. Without the flag, you could be anybody.
Oh, and it's worth noting that Slocum's the first solo sailor to make it around the world, so there's a little bit of novelty in his small vessel being treated as a ship by other sailors and officials. He kind of emphasizes that in other sections - being the captain and only crewman of an ocean-going vessel. How much any risk to Spray flying U.S. colors is real or imagined or just exaggerated for effect, I have no idea.
Anyway, it's a great book - if you're into this kind of thing, it's a really fun read.
