>>1821973This particular one is immediately under 4 feet of water 15 feet in, and this tunnel slopes down. when i took this pic I brought a big ole' spotlight hooked up to a lawnmower battery and I could see the collapse a few hundred feet in anyway.
Picrelated is a (mostly) dry tunnel that supposedly goes in 200 yards, but I've been avoiding going in here until I can get my hands on a flame safety lamp and someone to stand outside in case of a cave in.