RedactedNarrative: Vessel #1 was stationary, engine off, in forward gear.  The operator started the motor while in forward gear and the throttle mostly in the full position.  The motor revved and the operator was forced off of the seat and lost control of the vessel.  The vessel was out of control and spun clockwise traveling toward the west shoreline.  The operator stated that the vessel spun in circles approximately 10-15 times before becoming swamped which forced him into the water and the vessel sank.  The operator was able to swim to a nearby tree on the shoreline and remained there until he was rescued by another boater in the area.  The operator was not wearing a PFD.