I once found a cave alongside a creek. The entrance had been in the basement of some old building so that now a ruined brick wall contained the door into which I climbed. I had a flashlight and, after seeing a large body of water, went out and brought in my kayak. The water in the cave flowed from, and back into, an underground river. I paddled about, exploring the extent of the covered lake. It was cold, damp, and claustrophobic. The pitch black outside my little flashlight beam seemed eerily full of imagined rock formations, and I had the uneasy feeling that I would be sucked underground where the river disappeared. The water was icy still and black as oil. Outside, where the water reappeared in the form of a spring, it gushed through a 2-foot wide concrete hole in a column of pale aqua shining in the sunlight.