On July 20, 1997, about 1200 eastern daylight time, a Piper J3C-65, N98879, collided with water while practicing stalls over Lake Harris in Leesburg, Florida. The airplane was operated by the pilot under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions existed, and no flight plan was filed for the local, personal flight. The commercial pilot and one passenger sustained minor injures and the airplane was substantially damaged. The flight departed Eustis, Florida about 1140 on the same day. The pilot stated to the local authorities that he was demonstrating stalls to his son. He said that he had recovered from the first stall without incident, climbed to 2000 feet and initiated a second stall. While attempting to recover, the engine failed to return to full power when the throttle was advanced. The airplane entered a spin, and while recovering the right wing tip struck the water and the airplane cartwheeled and sank. The pilot and passenger swam out of the airplane and were helped to shore by a nearby boater.