What happened
During an instructional flight intended to prepare a student for a single engine sea airplane rating, a Cessna (type not specified) collided with the shore and a tree. The dual student, who held a private pilot certificate with a single engine land rating, was performing a practice step taxi across a lake.
The flight instructor reported that the student attempted to initiate a step turn while approaching the opposite shoreline. According to the instructor, the student used aileron input only and failed to use rudder input. Despite the instructor providing three separate directions to apply rudder, the student did not comply.
Upon the third request, the instructor took control of the aircraft. Fearing the aircraft would strike the shore and that increasing the turn rate risked capsizing the plane, the instructor reduced power and applied right rudder in an attempt to impact the shoreline perpendicularly. This maneuver was unsuccessful, and the aircraft struck the shore at an angle. The right wing subsequently caught a tree approximately 2 to 3 feet inboard of the wingtip.
Findings
The aircraft sustained substantial damage during the collision. The instructor noted that there were no mechanical issues with the engine or the aircraft prior to the accident.