Continuity mistake: At the end of the film the fleet were instructed to sail towards the burning vessel, which would have meant that they were travelling west - into the setting sun. Given the location of Montevideo on the River Plate it is somewhat dubious that the sun would set over the sea even at that time of year.
Continuity mistake: When the gun firing has ceased, the German boarding officer tells the British prisoners they will be freed in the morning. As they are whooping and cheering, Captain Dove of the Africa Shell goes out to view the harbour and in the melee loses his cap. When he looks at the scene his cap has reappeared on his head.