Flight 161 departed Miami, Florida, at 06:08 for a flight to Leopoldville, Belgian Congo. The flying boat landed at San Juan Harbor, Puerto Rico, at approximately 14:23. After refueling Flight 161 took off from San Juan, at 16:05 on a contact flight clearance for Port of Spain, Trinidad. Crossing the north coast of Trinidad at an altitude of 4,000 feet, a gradual let-down was started. Wind was calm, and lights to mark the landing area on the surface of the water were laid out on a 70 degree course. The approach was flown by a captain acting as first officer in the left hand seat. During the first approach he came in too high so he was forced to circle the landing area. During the second try, the Martin descended too low and contacted the water at more than normal landing speed and in a nose-low attitude at a point 1,25 miles short of the intended landing area. As the plane came to an abrupt stop in the water, the hull broke in two at a point about three feet aft of the hull step and the rear part of the hull was forced up and forward. Water poured into the cabin and major portion of the flying boat sank immediately. PROBABLE CAUSE: “(1) First Officer failure to realize his proximity to the water and to correct his attitude for a normal landing and, (2) the lack of adequate supervision by the Captain during the landing, resulting in the inadvertent flight into the water in excess of normal landing speed and in a nose-down attitude.”