Tanais

this monument in the area of Koum Kapi remembers the plight of the prisoners of war on the ship Tanais:

"Shortly after 2:30 A.M. on the morning of June 9, 1944, the British submarine HMS Vivid spotted the Tanais some 33 miles northeast of Piraeus. A short time later, the submarine’s commander, Lt. John Varley, ordered the firing of four torpedoes, two of which apparently hit the ship. Within a quarter hour, the Tanais was gone. None of its prisoners, who were locked into their quarters, had a chance of surviving." http://www.haaretz.com/news/features/this-day-in-jewish-history/.premium-1.597608

that's how all but 25 members of the entire Jewish community in Crete died (by mistake)