RedactedNarrative: Operator of vessel 1 shifted into reverse to leave the dock but the vessel went forward.  Operator added more reverse throttle causing the vessel to accelerate forward. The vessel hit the dock, rode over top of it and the bow flipped back over the stern.  The vessel was completely overturned pinning the operator under the vessel.  The operator was able to swim out from under the vessel.  After a complete inspection by a marine mechanic it was found  that the shift cable to the stern drive had come loose causing the drive to be stuck in forward.