The solo private pilot of the float-equipped airplane, was taking off from a remote lake for a personal flight under Title 14, CFR Part 91. According to the pilot of the helicopter that recovered the airplane, the accident pilot told him that he was taking off from the lake, and the airplane would not come up on step. He told the helicopter pilot that he didn't think he had pumped all the water out of the floats prior to takeoff, and that during the takeoff roll he lost control, and the airplane impacted the water. The helicopter pilot said there was substantial damage to the wings, fuselage, and empennage. The pilot did not complete an NTSB accident report form as requested.