According to the pilot, he completed a preflight inspection and estimated that there were approximately 5 gallons of fuel in the left main tank and "little or none" in the right main tank. He added that he departed with the fuel selector in the "Both" position. The before-takeoff checks were "good" and he performed a southerly takeoff. While turning crosswind, the engine stopped producing power, the airplane "wanted to stall," but it landed on the water "hard" and under control. The airplane then struck a dock, the floats collapsed, and the airplane continued into the woods which damaged the wings. The winds reported 12 miles west of the accident site were from 190 degrees at 6 knots. Other than the loss of engine power, the pilot reported that there were no problems with the performance and handling of the airplane.