The aircraft departed Melbourne Airport at 01:09 hours for Cambridge Aerodrome, Tasmania, on a special freight charter flight with a crew of two. The all-up-weight on departure was 26,200 lb. and the freight comprised 12 refrigerators and 61 cases of tomatoes. The weather forecast for Cambridge Aerodrome at the estimated time of arrival, 03:33 hours, was 8/8ths strato cumulus cloud base 2,000 feet, 2/8ths stratus cloud base 1,000 feet, drizzle, visibility 4 miles and wind light and variable. Launceston was designated as diversion airport for the flight. En-route to Cambridge Aerodrome the aircraft reported at the designated reporting points on schedule, and arrived over the Hobart “Z” marker at 03:22 hours at an altitude of 5,000 feet. The Cambridge weather at this time was 5/8ths cloud at 1,200-1,300 feet, 8/8ths cloud at 2,000-2,200 feet and visibility 3-4 miles. Under these conditions the aerodrome was closed, the night cloud ceiling minima being 1,950 feet, and the aircraft was instructed to hold on the holding pattern at 4,000 feet on a QNH of 1002 millibars. Just after 03:30 hours the weather improved to 8/8ths nimbo stratus cloud with a base of 2,200 to 2,400 feet and 2/8ths fracto stratus cloud in two layers between 700 and 1,400 feet and at 03:33 hours the aircraft was cleared to carry out an instrument descent on the Visual Aural Range (V.A.R.), commencing from the “Z” marker. The aircraft, which was not fitted with Distance Measuring Equipment, arrived over the “Z” marker at 03:34 hours and a left turn through 210ø was carried out back through the marker, intercepting the south-east leg of the V.A.R. at an angle of about 30ø. On passing the “Z” marker outbound the descent was commenced at 500-600 feet per minute at 115 knots with the undercarriage up. At an altitude of 2,500 feet a procedure turn to the right was commenced and the undercarriage lowered. A rate of descent of 200-300 feet per minute at 115 knots was maintained duringú this turn, which was completed at an altitude of 2,000 feet, at which stage the aircraft was again on the south-east leg of the V.A.R. and heading for the “Z” marker. The captain states that during the turn he “could clearly see large areas of water but no lights” and as the turn was completed “could see Seven Mile Beach but could not see the aerodrome or aerodrome lights” nor was there “any cloud between my position and Seven Mile Beach, but to remain visual I continued to descend at 1,000 feet per minute”. Shortly afterwards the aerodrome lights were sighted and at an altitude of 1,000 feet he “trimmed the aircraft and adjusted power to maintain a rate of descent from 200-300 feet per minute direct towards the end of the runway”. At this time, 03:39 hours, the captain, who was flying the aircraft and also operating the radio, called Hobart Air Traffic Control and gave his position and height and reported that the aerodrome lights were in sight. Hobart acknowledged and advised that the rotating beacon would be switched on. The captain replied “thanks” and a few seconds later found himself underwater. The captain surfaced some distance from the aircraft and on swimming back to it he found it floating in a nose down attitude but comparatively high in the water. There was a large hole in the nose of the fuselage and he swam in through this to search for the first officer but without success. The aircraft sank as he came out of the fuselage. The probable cause of the accident was that the pilot in command relied on inadequate external visual references for determining the altitude and paid insufficient attention to the instruments, particularly the altimeter. The irregular approach procedure carried out by the pilot in command deprived him of the opportunity to monitor the safe approach to the aerodrome through the correlation of time, height and position. This probably contributed to the accident.