I was with a group of RME'ers (cruser and others??) inside of the Globe Mine in MEG, AFC when it began to cave ~ 1/4 mile behind us. It was a very, very moist spring and there was alot of water in the shaft... Olly and I were walking in 6" or so of water, so our feet were freezing. All of a sudden those at the portal began yelling at us, at first we thought they were messing with us, however as I had my Cruiser parked with the headlights facing in the tunnel and we could see the rock sluffing off the side of the cave, damming the water in the bottom deeper and deeper. By the time we got back to the cave (trying not to run), Olly and I had to literally crawl through the little hole (much smaller in my mind ) and get out. I've been back since and its been cleaned out a bit... much safer when dry.
That was me and Brad... something (can't remember his last name!). That was definitely an interesting experience. My favorite was when Olly dived back into the collapsing mine, Indiana Jones style, because he dropped a sandal.