The pilot accepted a clearance to fly the NDB RWY 17 approach to the uncontrolled airport without altimeter information. This made the MDA 1,300 feet. The weather reported to the pilot was 800 feet overcast and visibility 2 miles at a facility 48 miles away. Weather at the airport was 200 feet overcast and 2 miles visibility. The light condition was dark night with fog and haze. The airport manager attempted to contact the pilot by radio when he heard the airplane pass over the NDB, but was unable. The pilot descended below the minimum descent altitude and impacted into trees and the Little River about 7 miles NNW of the airport. No mechanical anomalies were noted during the post accident examination of the airplane and its systems. About 8 hours after the accident a 13 year old passenger swam ashore and was later located approximately 1.5 miles from the site. At about the same time rescuers found the wreckage.