RedactedNarrative: Operator 1 was operating Vessel 1 near the east shoreline of Horsetooth Reservoir about 550 yards North of the Sail and Saddle Club. Operator 1 was operating his vessel in a careless manner. Changing directions and doing doughnuts on plane very close to the shoreline. Operator 1 then struck an object (believed to be a submerged rock) causing vessel 1 to take on water and eventually sink.