On the way back we spent more time inside, belowdecks, and while we didn't see a porpoise we did see some remarkable bird. It looked like a pelican, but it hopped up into the air, glided a bit, and then just ... cut its engines and dove, smashing hard into the water and vanishing underneath it before emerging a couple seconds later. My mother said she remembered reading about that bird in the local newspaper's report of what was migrating through the area, and that it was a relative newcomer to the Charleston area, although she didn't remember what kind of bird it was. She promised to look it up and either she forgot or we forgot to ask.
Also while sailing back we saw an oddly-shaped boat, with a huge, pretty squat profile to it, and wondered what it could be. My father remembered seeing it in the harbor in past times. We couldn't make out the ship's name, but 
bunny_hugger used her big, quality camera to take a zoomed-in picture of it and she was able to make out its name in the photograph, later on. It turned to be a boat designed for sailing cars, which apparently are made more in Charleston than I would have guessed before this.
My parents weren't sure we had gotten enough letterboxing in, and when they learned there was a letterbox reported planted not a mile from their apartment they were enthusiastic that we should go looking for it. We were skeptical that the box was there --- it had never been reported found, and the letterboxing web site said the person who planted it hadn't logged in in over a year, suggesting the box was defunct and the person had left the hobby --- but we drove past the spot where the box likely was and confirmed that it looked like the sort of place that would get a letterbox. So we returned to their home, got our gear, and bunny_hugger and I set off on foot.
We did find a spot, woods past a little park that's got a small pond and warning signs about alligators, and we feel very sure that we were in the right location. It just had all the right feel for a letterbox location. There just wasn't any actual box there. The last couple clues referred to items like twin pairs of tree stumps, and we could find only a single tree stump; and the references to fallen trees just didn't help matters since we could find spots where there were too many fallen trees for any to stand out, and none of them seemed to be the described ones. We had to conclude the letterbox had gone missing and the planter disappeared.
But it did give us the chance to walk around a bit near sunset and see some lovely marshland, as well as to see a good number of dogs and to get a feel for the squirrels of Charleston. They appeared to be mostly Eastern Greys, but they were smaller and scragglier than those we've got back home. Particularly, they haven't fattened up for winter, which is defensible when the winter is something that lasts for literally hours, but still looked funny. Also the squirrels were very aggressive; they spent a lot of time glaring at us and making threatening noises before running off. I feel like there's a history we don't know at work here.
We went out to a Thai restaurant for dinner. I forget where bunny_hugger had heard about it, but my mother identified its existence as something my father surely proposed. He likes the place, apparently, and I guess they don't get to it as often as he might like. Again I feel like there's a history we don't quite know at work here.
Back home we finally --- finally! --- got to giving my parents their Christmas presents, which were mostly books because those are easy to pick out and wrap and send in luggage, even if the wrapping on bunny_hugger's gifts were inexplicably chewed up while in flight. Also we got to give them a box of Fabiano's chocolates, which brought a gasp of delight from my mother, so that was a good bit of gift-giving.
My mother went to bed relatively early, but my father stayed up with us, talking a lot and listening to the Christmas music channel on their cable box. Their music stations included, besides songs, some pictures and various bits of trivia. Some were sound, like mentioning the big Christmas-industrial complex at Frankenmuth, Michigan. Some were dubious, including multiple and not-quite-compatible origin stories for ... oh, I forget which, now, but some Christmastime snack. There were some ads for their music service too, including one that offered the suggestion you should pick a music channel when you want to select your mood, which seems to come pretty close to the homunculus problem to me since surely wanting to have a particular mood is itself a mood, isn't it?
To our surprise --- we missed the exact moment --- the Christmas music station switched off just at midnight, at what anyone would have to admit was the end of the (non-Orthodox) Christmas season, the end the Feast of the Epiphany. We were delighted the music station respected the season so, and wondered about the Christmas music stations back home. When we got back, the main ones we'd been listening to had reverted to normal programming, although there were two Muzak channels still on Christmas songs. We missed the exact time when those channels went off the air.
It was getting pretty chilly at night, and when I closed up the window before bed I was sorry I hadn't closed it up earlier. We were dodging the second real cold snap of the winter back in Michigan, but that didn't mean South Carolina was going to stay warm.
Trivia: The secession convention which met in Charleston in December 1860 passed an ordinance reverting all state powers ceded to the United States back to the state legislature, with the exception of the power to impose duties and customs, manage the Post Office, and declare war, which it kept to itself. Source: Look Away! A History of the Confederate States of America, William C Davis.
Currently Reading: Washington Burning: How a Frenchman's Vision for Our Nation's Capital Survived Congress, the Founding Fathers, and the Invading British Army, Les Standiford.
PS: A Venn Diagram of the Real Number System, which isn't really a Venn Diagram, but it's just me reblogging a nice little (if flawed) picture. But you already knew about it if you're following its Livejournal Syndicate feed, or the raw RSS feed it started from.