Hey, what should we do with all our old tires? Burn them? Toss them in a field? Nah, let's chuck them down that pristine miracle of nature over there. Out of sight out of mind.

By the way, you should never try swimming in any underground water that you might find in a cave or old mine-shaft unless you're sure it's been explored and is safe. People die diving in because the water is so clear it looks like they'll be okay. There can be trapped gas retained by the surface tension of the water, it escapes and when you come up you've got no air to breath, it's all been displaced by methane or something. Also, fine silt can be stirred up, and you can become disoriented and not be able to find your way back to the surface. Totally blinded you don't know which way is up and accidentally swim deeper, or in the wrong direction. Probably a horrifying way to die.

I don't have to worry about it though because dark water scares the hell out of me. I always know there's some giant creature just out of sight observing me. My imagination gets away from me and I can't help thinking what the scariest possible thing to swim in to view might be... Like a huge mutant catfish monster with three sets of human arms or something, and, it's got it's offspring embedded all over it's back in little cavities with their squirming arms and heads sticking out, like those gross south-American frogs. They're always just far enough in to the darkness that I can't spot them.