This happened while pulling out where I'm from in Idaho. I pulled up onto the trailer, climbed over the bow and winched up the last few inches. I was standing on the bumper holding on to the tailgate while my partner drove up the launch when the gate popped open and I got rolled up underneath the trailer. I was wearing a heavy PVC fishing parka so it wedged me under there like a cork. My buddy got the trailer off me but I cracked three ribs and ruined my parka.
I've stood on the bumper a hundred times before this but not since.