Details the preparations, section-by-section assemblage, and materials used for casting a plaster of Paris mold of the faint marks left by a sunken (5th to 7th century old) Viking ship at Sutton Hoo (England) in order to produce a fiberglass replica for museum purposes. The remains were in extremely damaged condition but the cast began in July 1967 would provide a record of the size, proportions, and profile of the ship. A similar method was used to mold the waterlogged timber remains of a 10th century boat found on the Kent marshes in 1970; this work is also described. The advantages and disadvantages of using plaster of Paris as compared to rubber latex and polysulfide rubber are assessed.