The pilot had flown the aircraft to Cape Capricorn with the intention of landing on the beach. He had been landing on the beach there for about ten years. Prior to the landing he had carried out a low level inspection of the area and satisfied himself that it was suitable. The aircraft touched down about 40m from the waterline. However, during the landing roll, when the aircraft was about 20m from the waterline, the pilot became aware that the area in front of the aircraft was covered in water. When the aircraft entered the water, which was estimated to be 50-75mm in depth, the nose leg was bent backwards and the aircraft nosed over and came to rest inverted. Neither of the occupants received any injuries. The pilot reported that local fishermen advised him that a couple of times each day a larger than normal wave causes the beach to be covered in water to a greater extent than the normal action of the waves.