The inadvertent ground loop/swerve by the second pilot during the landing roll, and the first (check) pilot's inadequate supervision of the second pilot, which resulted in a loss of control and substantial damage to the airplane. Factors associated with the accident are the second pilot's improper upgrade/transition training by the company check airman, the second pilot's lack of experience in the accident type airplane, the operator's lack of surveillance of the training process, and a crosswind.

The pilot-in-command's failure to identify the swells prior to landing. A factor was the water swells.

THE INCIDENT WAS CAUSED BY THE PILOTS IMPROPER COMPENSATION FOR THE WINDS. FACTORS WERE THE MICROBURST, THE ROUGH WATER, AND THE PILOT'S INADEQUATE EVALUATION OF THE WEATHER CONDITIONS.