MS Transpet was a tanker of United States and Panamanian registry. Laid down as MV Avoca and acquired by the Maritime Commission (MARCOM) on a loan charter basis and renamed USS Petaluma (AOG-69), she was to be a type T1 built for the US Navy during World War II. She was named after the Petaluma River, in California. Petaluma (AOG-69) was never commissioned into the US Navy.
Petaluma (AOG-69) was laid down on 14 February 1945, under a Maritime Commission (MARCOM) contract, MC hull 2629, by the St. Johns River Shipbuilding Company, Jacksonville, Florida; acquisition by the US Navy was cancelled 26 August 1945.
Petaluma was launched on 5 May 1945, and was about 85% complete when, due to the end of World War II, the ship's US Navy reassignment was canceled. Although initially restored to her original name of Avoca by her original owners, the unfinished ship was completed by the Maryland Drydock Company in Baltimore, Maryland, in October 1947, and sold to the National Petroleum Transport Corporation where she was renamed Transpet.
From 1947 until 1951, Transpet flew the US flag. In 1951 Transpet was registered under the Panamanian flag and placed under the operation of D.K. Ludwig of New York for the British-American Oil Company.
On 29 October 1951, the tanker departed Montreal for Halifax, loaded with 1500000impgal of gasoline and kerosene. The following day, the ship suffered an explosion in the engine room while in the Gulf of St. Lawrence. Two seamen were killed in the blast; the other eighteen members of the crew abandoned the sinking ship and were rescued by the British ship Ottinge and landed at North Sydney, Nova Scotia.
In May 1954, the Minneapolis-Honeywell Regulator Company announced that its "sea scanar" device had located the wreck of Transpet at a depth of 120feet about 13nmi off Miscou Island. It was the first time the "sea scanar", which had been in use as a fish finder off the West Coast of the United States, had been used in a salvage operation and the first wreck located using it.