While flying east, the pilot put the helicopter into a slip and descent to the north (left) to look at something closer on the left side of the helicopter. During the descent the helicopter hit unseen power lines on its left side, breaking the power lines and seriously injuring the passenger in the left seat. The pilot landed nearby and called for medical assistance for the passenger. The passenger later stated they had been hunting hogs at the time of the accident and the hog they were after had gone under the helicopter from the right to the left and "the pilot put the helicopter into a left slip" and that was the last thing he could remember about the flight.