So, it's not like they're *trapped* inside a volcano. The caldera is under the water, and the sharks seem to prefer to swim into it, for some reason.

A clue might be found in the trailing bits that are attached to the sleeper shark in the video. That's a parasitic copepod (a small crustacean) that's burrowed into its skin. Perhaps the sharks are swimming through the hot, acidic water to kill external parasites?

Looks like a fire marshall's nightmare

Here in the Western part of the country, such caves would have a lot of granite, and the cool air might carry lots of radon gas.

I need to buy that brushed steel-looking contact paper. I'll cover my car, and pretend it's a DeLorean!

. . . a DeLorean minivan.

Another take on this was posted years ago.
Somehow, I love these.
http://www.neatorama.com/2015/11/29/Sad-Sad-Jingle-Bells/

Why does she dress like Jesus in "Godspell"?

Seeing the picture, you can immediately tell that she's in Japan. The restroom floor is immaculate!

I just try to keep conversation generic until they go away. Often from boredom.
I once ran into a person in the grocery store who started talking with me. She seemed to remember me, and knew a bit about me, I think. We talked for a couple minutes, and then I was out of ideas. I made my confession that I didn't know who she was, and she said that we spoke last week in the same store, next to the eggs.

All I could think was: "People remember other people that they just run into?"

Here in New Mexico, you can bury a dead human, and it will be intact (if a bit dry) when you dig it up 100 years later.
OK, I don't know that for a fact, but it seems about right. Our "soil" is actually adobe reddi-mix.

That's why you should never engage the Flux Capacitor unless you are in a location that will be deserted at the time of re-entry!

Wow. That was fascinating, and very informative. Lots of information presented in a way that kept my attention.

I assume the other kids were able to replace their fluids naturally, and so had no long-lasting damage.

So, had the Ghostbusters been more clever, instead of Mr. Staypuft, New York would have been menaced by the Attack of the 50-foot Lingerie Model.