Operator and wife entered Lake Ontario via Sandy Pond Channel.  The conditions on the lake were a little windy and choppy.  After a half an hour, the weather conditions deteriorated and the operator decided to return.  Operator kept vessel close to the red buoys, but as they approached the second buoy the engine became fouled in the sand.  The operator jumped into the water and the wind and waves pitched the vessel from the water into some unmarked boulders.  The passenger sustained injuries to her legs but not beyond first aid.  With the passenger's assistance, operator was able to free the vessel from the rocks, but not before sustaining significant damage to the boat.