I've already mentioned this elsewhere today but I thought it would be worthwhile covering it here, too. Yesterday, I read this article on the BBC about a Derbyshire quarry commonly known as the "Blue Lagoon":
It's disappointing that the quarry has had to be dyed black to ward off people from swimming in it. From what I've heard, the area is well-signed to inform people that the Blue Lagoon is toxic and should not be approached, let alone swam in. The water might have appeared beautiful but as we all know, all because something is beautiful does not automatically make it beneficial to you.