The private pilot reported that while practicing beach landings he made a low, slow pass over a beach to check its suitability for landing. After determining the beach was suitable for landing, he made a left turn to the beach for landing. He added flaps in the turn, and as he turned final, he realized he was too low and too slow. He added power, but the airplane impacted terrain short of the intended landing area. The landing gear collapsed, and the wings and fuselage impacted the ground. The pilot stated there were no known mechanical anomalies with the airplane prior to the accident.