A CAT 330B BACKHOE WAS BEING USED TO DREDGE SAND FROM A POND. THE GROUND SUPPORTING THE BACKHOE COLLAPSED CAUSING THE BACKHOE TO TIP INTO THE WATER. THE OPERATOR EXITED THROUGH A WINDOW OPENIN G. THE OPERATOR INCURRED A LACARATION TO HIS LEFT FOREARM. THE LACERATION WAS CLOSED WITH STITCHES AT THE ALBERT LEA MEDICAL CENTER.