The float-equipped airplane operating as a Part 135 on-demand charter was substantially damaged at about 1320 Pacific time after striking powerlines while on final approach to Killkarney Lake. Neither the Commercial pilot nor his two passengers were injured. Visual conditions prevailed. The pilot subsequently reported that he flew over the area at approximately 500 feet AGL before attempting to land. While on final approach, the airplane was at approximately 50 feet AGL when he saw the wires. The pilot reported that he immediately added full power to raise the nose when the top wire went over the top of the floats, catching the float struts. The pilot stated that the wire broke off the right side but was still entangled on the left side, pulling the airplane down. The pilot reported that he then pulled the nose up before impacting the water.