I’m a cyclist.
I’m a balloonist.
Tonight I get to be one of the few people in the country (& therefore probably the only Doper) to marry those two & take my bike up on the balloon in one of the few bike/balloon races in the country.
I’m wondering, and yes my brain iz weird (hey I’m a doper), how big is the camera and its related equipment?
Lots of reservoirs in Europe have submerged towns as well, I’m having vague and completely unrealizable by me thoughts about documentaries on their ecosystems and what kind of different biotes you find on the old town vs the rest of the lake.
This sounds a bit like a real-life version of a quirky hobby that I’ve developed recently. I’ve discovered that I am perhaps a budding roadgeek, and lately I’ve started to get into watching driving videos.
These are videos that people post on YouTube, filmed with dashboard cameras, of drives they have taken on various highways. The footage will be speeded up by a couple factors, so it’s not exactly real time, and be accompanied by music. Often they’ll also add little trivia notes about the highway being driven or the cities being passed through. Here is a typical example (YouTube link).
Understand that these are not dashcam videos of crashes or traffic stops or anything particularly exciting. They’re just videos of perfectly ordinary drives on perfectly ordinary roads. There are hundreds of such videos on YouTube, and gobs of people making them.
It’s remarkable enough that such things exist, but what’s even more remarkable is that I have become ridiculously fond of watching them!
I’ve discussed my Lube Smithying pastime before. Didn’t get a lot of traction. Maybe because it involved lube?
I make archery bows for a hobby. My particular niche is studying performance and tracking energy losses. As far as I know there is no one else on the planet who has studied it as extensively as I have or done the amount of testing I have done. To say I have taken it to another level is an understatement.
When I was a kid, I would create fantasy trips around the world connecting major cities, then connect the paths by finding flights using the Official Airline Guide in the library.
I know I’m not the only experienced skydiver on the boards, there are a few others but not too many.
I like to visit ghost towns here in New Mexico. I have a book on the subject and I enjoy reading about their history and visiting what’s left of them. There are quite a few mining towns that sprung up almost overnight, thrived for a few decades then died when the mine stopped producing. Some of them had thousands of residents, saloons, banks, brothels, hotels etc.
Some of them look like the stereotypical ghost town from movies, some have nothing remaining except the foundations of a few buildings. It’s interesting to me how a town can spring up from nothing, attract thousands of people, have thriving businesses and then completely die out with almost no one and nothing left, in just a few decades.
I love to take lists of any four objects and divide them into seasons. Seriously.
For example, I once bought double chocolate, apple pie, raspberry tart and cinnamon bun candles. Winter, spring, summer and autumn.
I have found a kindred spirit. 
In cleaning out some old boxes last winter I came across some of my old maps. Not sure what to do with them - I don’t really want to toss them, but I don’t think I want to share them, either.
You can come out to CA where the lakes are dry and just walk around the old towns now.
I read a lot of secondhand and library books. What began as a quaint fascination with what the previous readers left behind as bookmarks has grown into a somewhat creepy scrapbooking pastime. Random notes and letters, family photos, receipts, lists, - so incredibly personal in nature, many of them. I found it difficult to throw away nice family photos - even of these strangers, and when I’d acquired a shoebox full after a number of years, well, it was time to organize (there is a tremendous period of boredom one goes through after divorcing).
I’m not the only one, though - I recall reading somewhere - perhaps even here? - another person admitting to devoting time to this particular collection hobby.
That’s awesome.
Any photos you can share?
It’s small enough to carry easily, even the really old video stuff I have. My camera is an old Aqua-Vue, similar to this. The video is good, but when it’s deep I need a lot more light. I’m experimenting with a weighted light box (waterproof container with uber-bright, battery driven led lights). So far it has remained waterproof at 50 feet (for 30 minutes), but I’m still getting it figured out. I should probably just pony up the bucks for a good infrared model, but I’m cheap. The newer Aqua-Vu’s are a lot better and lighter, but I haven’t sprung for one yet.
Laggard; I have almost no pictures, but I will try to upload the (crappy) video of the critters crawling on the lens this weekend. It’s large and I’ll need to tie up the computer for awhile to upload it. I promise to get to it in a few days though. I don’t know what they were, but they were small, out of focus (on the lens) and numerous. It made me rethink an earlier desire to scuba dive on these spots. 
I also did the “draw an imaginary city” thing (actually usually an island or an entire country), with roads, rivers, mountains and oceans.
Then I would draw very complicated and detailed currency (paper money) for imaginary countries, or even for the US. Nothing good enough to pass at the gas station, but my money makes our greenbacks seems so boring.
I’d also design coins, seeing how much stuff I could put into a small circle while keeping inscriptions and dates legible.
Guitar geeks do this, but I suspect I am one of the few/only on the SDMB: I collect playing experiences for old guitars. I try to find cool, old examples of guitars I haven’t played and check them out. Old Gibsons, Martins, Stella blues boxes, a Selmer Maccaferri like Django Reinhardt played - interesting guitars that have a place in this history of the instrument, and help me experience different tones and responsiveness.
I’ve played some celebrity guitars, but I really only care if it is a make or model I haven’t experienced.
Definitely a niche hobby.
If you’re ever over here in England, you can search for Nether Hambleton underneath Rutland Water (a reservoir.)
I search Google Maps Street View to find the locations of photographs. For example, this image from the new Man From UNCLE movie. After a lot of searching, narrowing down countries and then cities and then recognisable landmarks, I found it was here.
I had to give it up (temporarily?) when I moved, but I used to own a Linotype that I restored over the course of a few years. I’d just head down to the garage, pick a typeface and layout, and just cast type for a few hours. Never printed with any of it even though I also owned a large letterpress. I just like casting type.
I thought water was opaque to infrared light.