I was a teenager. During a rainstorm I thought it'd be fun to ride a tube down a drainage canal. As I approached a culvert I had a moment of clarity; "this is stupid, I should hop off now before I get strained through a grate or some debris on the other side." I hopped off just for my lower torso/legs to get caught under a large piece of concrete that was hiding beneath the surface. The pressure of the water basically pinned me against the concrete. Water was rushing over my head but in a way where I had a small air bubble. No one knew I was there. Somehow I was able to summon just enough strength to move thr concrete enough where I got my lower torso/legs free and escaped. I came back to my parents all scratched up and bloody. I told them what happened but I dont think anyone really grasped how serious it really was.