I caved with the NSS for about 5 years.
In 1983, I was on an expedition that was mapping Fisher Ridge Cave. It's now part of the Mammoth system. Back then it was separated from Mammoth by another system.
I went in with 4 other guys. Two guys brought in tools to widen out a hole in the wall that had been felt to be blowing, so it was assumed there was more cave on the other side. I went with a another two guys back to the furtherest part of the known cave and map it using a compass and inclinometer. While I was back in a passage about 100 meters, my carbide light got blown out. I relit it and it promptly blew out again with a breeze coming the other direction. When I came back out the two guys with me were white-faced with fear. There must me one hell of a storm going on, and they knew we had to skedaddle. As we retraced our steps, dry cave started to drip. Drips were now streams. Streams were torrents. We had about 4 hours of this before we reached the exit. There was no sign of the other two guys. I was the junior of the bunch, so they had me go out first. The egress was through 100 meters of hand-and-knees crawl with influx water. The water was coming up fast. I ran out of ceiling with about 10 feet to go before daylight. I sucked some air off the roof and went for it. The two guys behind me found a crease and floated out on their backs. The two guys behind them didn't make it out.
I was told to stay at the entrance and help the two guys if they tried to make it out, while the other two guys went for help. While standing at the entrance in the rain, I heard an ominous rushing sound and look back up the stream in the gathering gloom of twilight and saw a 3 foot wall of water coming down the valley. I threw myself on some roots and managed to get up out of the entrance before I got sucked in. At this point, the two guys still in were either drowned or they had gone deep and high in the cave and were safe. I went up out of the ravine about 50 meters, stripped off my wet gear and got under a poncho. Another thunderstorm came through about 2200. All of a sudden I heard the back of my neck sizzle and before I could investigate, lightning struck an oak tree about 10 meters off.
That was enough for me. I met the rescue team about halfway back to the road and told them there was nothing to be done at the entrance. It was dumped shut. I got to go back and tell one of our fellow cavers that her husband of ten years and her current lover were flooded in. My buddy and I stayed up with her at a Carters restaurant all night. At first light, I was packing for the rescue trip when I was informed I was scratched because of obvious fatigue. My buddy went. There was another entrance to the cave and conceivably the two missing cavers could be reached by that route. About noon the rescue team showed back up with the two guys. They had been about 15 minutes behind us, and seen a wall of water coming down the entrance passage and closing it off. They beat it back, but took a wrong turn and almost had the water get ahead of them. They finally made dry cave after an hour or two.
NSS cavers know to carry a big leaf bag and three plumbers candles as a latch-ditch measure. You crawl into the bag, sit with your knees up around your chin and light a candle. It's enough heat to keep you from dying from hypothermia. The two guys were down to their last stub of candle when found-- 15 hours.
