Shortly after takeoff at an altitude of about 50 ft, the engine lost power. During an emergency landing, the airplane clipped some trees, touched down in a field, and slid until it impacted a row of trees. An on scene investigation revealed about one quart of water in the fuel system. Examination of the fuel tank filler necks revealed corrosion. The right tank fuel filler neck also had pitting. When tested, the right fuel cap and seal area allowed leakage of an undeterminable amount of water. Examination of the fuel tank bladders revealed wrinkles. The airplane's maintenance records indicated that AD 84-10-01 and AD 83-13-01, regarding inspection of the fuel filler neck and seal area and the fuel tanks, were not performed during the last inspection. The airplane was kept outside and it had not been flown for several days before the accident. Snow had fallen on the previous day. The pilot said he did a thorough preflight, which included draining the fuel tanks and checking for contamination, but no contamination was evident.