Raft tipped, I fell over highest side. Raft came down on top of my head with helmet, crunching me against rocks causing severe knee contusion and deep laceration rendering left leg immobile. I was pinned underwater under the raft. Went down rapid under the raft. Used pre-rafting safety lesson to find the edge of the raft and grab the line to be pulled back in raft. EMS contacted and trip was aborted. EMS & Fire department performed backboard river rescue up mountain to the ambulance on the road. Injury required both stitches & staples, and crutches. Wound infection due to resistant bacteria warranted 10day hospitalization for IV antibiotics to avoid sepsis.