Standing near the seawall in Port Arthur in 1963, 8-year-old Gilbert Smith waved goodbye to his father as he sailed away on the Marine Sulphur Queen, a converted T-2 tanker, bound for Norfolk, Va.

In Beaumont, Texas, last week a U.S. Coast Guard board of inquiry sought to solve the mystery of the Marine Sulphur Queen. A 523-ft. converted tanker, the Queen left Beaumont on Feb. 2, bound for ...