Shin'yō Maru was a cargo steamship that was built in 1894, had a fifty-year career under successive British, Australian, Chinese and Greek owners, was captured by Japan in the Second World War, and sunk by a United States Navy submarine in 1944.

[12] In 1937 Tung-Tuck passed to the Lee Yuen Steamship Co, who renamed her Chang Teh, but sold her on before the end of the year.

[14] In August and September 1944, Allied intelligence intercepted Imperial Japanese Navy radio signals about Shin'yō Maru's intended movements.

Fleet Radio Unit Pacific (FRUPAC) interpreted the signal to say that she would be carrying "750 troops for Manila via Cebu".

[14] On 7 September her crew closed and secured her hatch covers, and she left port in a convoy[15] comprising four cargo ships, two tankers, and an escort of two destroyers or torpedo boats.

On 7 September Paddle found the convoy about 10 miles off Lanboyan Point on the Zamboanga Peninsula of Mindanao.

When the convoy was within two or three miles of Zamboanga Point, Paddle got into position and fired a spread of four torpedoes at her, two of which hit her in her holds.

The Japanese escorts then started unsuccessfully depth charging Paddle, but she dived deep and escaped serious damage.

[16] The two torpedoes that hit Shin'yō Maru killed or wounded many of the PoWs in her holds, and some of her Japanese crew and guards.

The surviving ships of the convoy launched boats to rescue Shin'yō Maru's crew and guards.

[15] In 1991 the Seychelles Postal Service issued a set of four commemorative stamps featuring historic cargo ships.

On 7 September 1998, the 54th anniversary of the sinking of Shin'yō Maru, a plaque commemorating the victims of the massacre was dedicated in San Antonio, Texas.

The town of Sindangan, Zamboanga del Norte, dedicated a memorial on September 7, 2014, on the 70th Anniversary of the incident, remembering the victims and survivors of the Shinyo Maru, as well as the townsfolk who extended help.