In the pre-take-off briefing the instructor advised the student that during the flight they would conduct an inspection of the power lines crossing the Herbert River. The student subsequently flew the aircraft, in accordance with the instructor's directions, at about 100 feet above the river. The instructor was aware of four power line crossings. After passing the first, and when en-route to the second, the pilots heard a scraping sound and the aircraft slowed. Despite the attempts of the pilots the aircraft nosed down and subsequently struck the surface of the water at a shallow angle. Investigation revealed that the aircraft had collided with a power line, the presence of which was unknown to the instructor and had not been seen by either pilot. One of the supporting poles was obscured by trees, while the other pole was located approximately 350 metres across the river in a sugar cane plantations. All the wires were estimated to be 100 feet above water level.
