I was walking backwards along a dock in Sitka, Alaska when I was in my 20's, waving goodbye to a mate leaving on a boat. I fell through the piling hole (situated in the middle of the floating dock), hit my head on the rail as I went under. I came up for air, and there was just weedy styrofoam. My friend dove off the departing boat and pulled me out from under the dock. I had a huge bone bruise on the side of my jaw for 4 months. 
  
The looks I got.