The Shinyo Maru: An Explosion, and Survival, for Some POWs, by Lee Gladwin

Vincent McDiarmid died on this ship.
On August 14, 1944, a Japanese naval message was intercepted on its way from Manila to Tokyo:
I have held preliminary negotiations with the Naval authorities in Manila in regard to the cargo of the Shinyo Maru As a result, it was decided to unload the rice and cement at Zamboanga and the miscellaneous goods, ([iron ?] products, etc.) at Manila. (I understand that the Shinyo Maru is now at anchor at Zamboanga. It is to be put to urgent use by the Navy, and it will therefore be absolutely impossible for it to sail to the Davao or Palau areas.)
An intercept of August 18 ordered that "Shinyo Maru is to proceed from Zamboanga to Cebu and then transport something on to Manila." According to a September 1 message, the "something" was "evacuees from Palau." A subsequent message on September 6 stated that the C-076 convoy would depart for Cebu on September 7 at 2 a.m. In that convoy would be the Shinyo Maru transporting "750 troops for Manila via Cebu."
At 4:37 p.m. on September 7, Lt. Comdr. E. H. Nowell, skipper of the U.S. submarine Paddle, sighted the convoy off the west coast of Mindanao at Sindangan Point and prepared to fire two torpedoes at Shinyo Maru.
Crowded into the foul and steamy holds of an unidentified ship were 750 U.S. POWs, most of them survivors of POW Camp #2-Davao, Mindanao, Philippines. Since February 29, 1944, 650 officers and enlistees labored on a Japanese airfield at Lasang. The other 100 had similarly worked on another airfield south of Davao. All 750 were marched shoeless to the Tabunco pier on August 19. On August 20, they were packed into the holds of the ship.
Late in the afternoon of August 24, the ship arrived in Zamboanga. The prisoners had no idea of where they were until the men who went topside to empty the latrine cans returned to tell them. "By this time the men were all very dirty [and] many suffering from heat rash and frequent blackouts," recalled 1st Lt. John J. Morrett. The "Japanese allowed the men up on deck twice to run through a hose sprinkling salt water." Morrett commented. "It was hardly a bath but helped considerably."
After ten days of waiting in the harbor, they were transferred to the Shinyo Maru on September 4. On September 7, hatch covers were placed more closely together and secured by ropes to prevent lifting from below. They sailed for fourteen hours without an air raid alert, and many "felt that the worst part of the journey was over."
"Suddenly," Morrett recalled, "there was a terrific explosion immediately followed by a second one," and "heavy obstacles came crashing down from above." Dust filled the air, and bleeding men lay "all over each other in mangled positions, arms, legs, and bodies broken." He struggled up to the deck and found it "strewn [with] the mangled bodies of Japanese soldiers."
Nearby, surviving Japanese soldiers fired at Americans swimming in the water or shot at those struggling up from the holds.
Morrett dove overboard and swam ashore. While swimming, he heard "a terrific cracking sound as if very heavy tissue paper was being crushed together, then the boat seemed to bend up in the middle and was finally swallowed up by the water." Friendly Filipinos and members of the "Volunteer Guards" assisted him and the other eighty-three survivors in returning to the United States.
The death of Shinyo Maru was duly noted by a Japanese cipher clerk at 1650 hours on September 7, the victim of a "torpedo attack." An intercept of September 10 reported 150 Japanese army casualties. Lt. Commander Nowell later reported that "this is probably the attack in which U.S. POWs were sunk, and swam ashore."
On December 31, 1944, a note was added to the message of September 6 that Fleet Radio Unit Pacific (FRUPAC) interpreted as ""SHINYOO MARU (750 troops for Manila via Cebu." In pencil was written: "FRUEF (31 Dec '44) gets 750 Ps/W"! FRUPAC misinterpreted this crucial part of the message with fatal consequences.