Royal Navy ships, especially the larger capital ships and cruisers, did have one or two cells aboard. However, these were used solely for the punishment of defaulters, and were not used for POWs. Instead, rescued German survivors would be housed in one of the ship's messes, with officers in the cabins of the RN officers. Sentries would be on guard outside the compartments containing prisoners. Prisoners were generally confined to quarters, with the occasional walk on deck. Ships that rescued German survivors would carry on the mission that they'd been carrying out beforehand - the most common source of prisoners was from submarines sunk while attacking convoys, and escorts could rarely be spared to take prisoners back to land. After the sinkings of the Bismarck and the Scharnhorst, the ships carrying survivors returned to the UK along with the rest of the forces responsible for the sinkings.