According to the pilot of an amateur built Searey amphibian airplane, he departed Eustis, Florida about 1420 and flew towards Lake Dora, Florida, to do a water landing. The approach onto Lake Dora, was normal. As he touched down he looked and realized that he had not retracted the landing gear. He applied full power and full aft elevator, however the drag from the landing gear did not allow the airspeed to increase and the airplane came to a rapid stop, and sustained substantial damage. The pilot further stated, that he had good instruction, and has flown many different airplanes, "I just made a bad mistake that I hope never happens again."