Tamahoko Maru

SS "Tamahoko Maru" was a Japanese passenger-cargo ship, used as a hell ship, which was torpedoed by submarine on 24 June 1944, carrying 772 Allied POWs of which 560 died.
Service history.
"Tamahoko Maru" sailed on 20 June 1944 with 772 POWs (197 British, 42 American, 258 Australian and 281 Dutch) from Takao for Moji in convoy HO-02. There were also some 500 Japanese soldiers on board. 
On 24 June 1944 at 11:50 pm, in the Koshiki Straits 40 miles SW of Nagasaki, the "Tamahoko Maru" was torpedoed by and sank in less than 2 minutes at 32-24N, 129-38E.
An escort picked up the Japanese survivors and left the POWs in the water, to be picked up the next morning by a small whaling ship, which brought 212 survivors to Nagasaki. They spent the rest of the war in the Fukuoka 14 prison camp. The other 560 POWs, 35 crewmen and an unknown number of Japanese soldiers were lost.