MS Rio de Janeiro (1914)
MS Rio de Janeiro was a German motor ship and a cargo ship, owned by the shipping company Hamburg Süd and home ported in Stettin. She was launched on 3 April 1914 as Santa Ines and later renamed Rio de Janeiro. She was requisitioned by the Deutsche Kriegsmarine for transportation of troops 7 March 1940, before Operation Weserübung, the invasion of Norway and Denmark, began on 9 April 1940. 
Invasion of Norway 
The secret plan for the ship was to arrive at Bergen right after German troops had captured the town. On board Rio de Janeiro there were a total of 50 crew and 330 soldiers. Her cargo consisted of six 2 cm FlaK 30 and four 10.5 cm FlaK 38 anti-aircraft guns, 73 horses, 71 vehicles and 292 tons of provisions, animal feed, fuel and ammunition.
The ship left Stettin on 6 April 1940 at 3 AM. Two days later, at 11.15, only hours before the attack on Norway began, a surfaced submarine was sighted off Lillesand. At first it was thought to be a German submarine, but it turned out to be a Polish submarine under British command. The submarine signalled for Rio de Janeiro to stop, and the order was followed. Captain Grudzinski, of the Polish Navy, ordered to bring the papers of the ship over to the submarine and surrender, or the ship would be sunk, but nothing happened. The Polish submarine ORP Orzeł then torpedoed the ship, and she took in water and sank. The crew and soldiers on board began to jump into the sea. At 12.00, an aircraft from the Royal Norwegian Navy Air Service started circling around the sinking ship. At 12.50 the submarine torpedoed the ship a second time, from a submerged position. The torpedo hit the ammunition depot, which caused an explosion. About 180 survived the sinking, and were rescued from the sea and brought by local vessels to Lillesand and Kristiansand; roughly 200 did not survive.
Norwegian officials were told by survivors that the ship's destination had been Bergen. The fact that there were horses on board and that many of the dead and survivors were wearing military uniforms, lead to alarming of central authorities.
The wreck 
The wreck of Rio de Janeiro has never been found, its exact position is unknown.
-  Divers site about MS Rio de Janeiro (Norwegian)