The ground loader had fueled the airplane from the airport fuel truck. He stated that the flight crew did not sump the fuel tanks after they were fueled. Immediately after takeoff the right engine lost power, the right wing lowered to about 90 deg, and the airplane impacted the ground adjacent to the runway. Then forward fuel tank, which provides fuel to the right engine, was found to contain about 8 gals of a heavily contaminated mixture composed of water,