The wheel-equipped airplane sustained substantial damage when it collided with the ice-covered surface of Lake Clark and sank at about 1110 Alaska time. The Commercial pilot and one passenger sustained minor injuries; the remaining three passengers received fatal injuries. Instrument conditions prevailed at the accident site. The accident pilot later reported there were no mechanical problems with the airplane. He related he was flying low, a few hundred feet above the lake in blowing snow and whiteout conditions, when the airplane collided with the surface of the lake. The accident airplane sank in water estimated at 800 feet deep.