It happed about five years ago (2017). They closed the park down due to lightning strikes on the radar, but it wasn't even raining yet. You have to understand that the topography of the area is not only hilly, but funnels down towards the front of the park. The front entrance of the park is a large tunnel. We were exiting the park and suddenly it started filling up with water. Then the heavens started opening up and the tunnel filled way quicker than I thought was possible. We had to head back towards the park end of the tunnel and made it out ok, but it was close. It went from a few inches to multiple feet in about 2 minutes. We were traveling with another couple that has an autistic son. He had a panic episode after the tunnel incident and we had to stop to calm him down. They exited us out of the left side of the park using a service exit, but in the 20 minutes or so that it had been raining the entire parking lot was a river. It varied from ankle deep to above your knees. We were all crossing this mess in a large crowd like a herd of water buffalo, when a person 'upriver' from us slipped and crashed into a number of people. The young daughter of the couple we were with got knocked loose and got swept down river with a few others. I was closest and jumped in after her with her mom about two seconds behind me. We all got funneled into a flooded gully and after about a 100ft or so it got shallow enough that a few people were able to get a foothold and start a human dam that caught the rest of us. Luckily, a stranger grabbed the girl before we even got anywhere near her. We got everyone out, but then to add insult to injury it decided to start hailing. We found out afterwards that there was apparently a tornado nearby as well, but we never saw it or heard any sirens. Not my favorite experience in a park.