20160313002209I

Certified flight instructor (CFI) was instructing a student pilot that had performed 2 short field takeoffs and landings that the student was rough on the controls. CFI was going to demonstrate how to set up and, especially, how to stabilize the final approach. CFI and student started check list but gear was delayed when CFI and student lost sight of other aircraft and did not reacquire aircraft until it was turning base to final. At one point the student thought he saw another aircraft on final but it was a boat on the lake and there was haze over the lake. These two circumstances caused CFI and student to divide their attention between seeing and avoiding other aircraft and performing the before landing check list. CFI was flying aircraft which was on base and continued to increase flaps, demonstrating a stabilized approach with proper airspeed and glide path control. CFI?s attention was concentrated on instruction and being sure the aircraft ahead cleared the runway before landing and the touchdown point was identified and because it was short field the CFI kept some power on till touchdown, which was on the spot selected. The CFI and student did not hear the gear warning horn nor did the red light come on. Aircraft then impacted the runway causing both propellers to strike the runway and aircraft landing on its belly. Neither CFI nor student was injured.