Located in Wimberley, Texas, Jacob's Well is somewhat of a natural phenomenon, and a deadly one at that. It is the largest underwater cave in the state, and if underwater caves aren't enough to scare you, maybe the fact that it can swallow professional divers whole will. Jacob's well might look like a peaceful spring from the outside, but it's actually an impossibly deep, black hole containing four chambers measuring 190 feet.
Ten known divers have been taken by Jacob's Well, and that's just the ones we know about. What most thrill seekers don't realize is that the chambers become tighter the further you go down. It's highly likely you would be trapped within the depths and never be seen again. For those who really want to see it, there's definitely nothing wrong with just dangling your legs in for a minute.