The real HMS Amethyst was used at the start of filming. A special effects explosion was made too big and blew a hole in the hull, flooding the engine room. Amethyst was sent to the breakers and HMS Magpie was used for the rest of the film.
HMS Amethyst sustained more damage during filming than during the actual battle.
The River Orwell, which runs between Felixstowe and Harwich, in Suffolk, England doubled as the Yangtze River during the making of this film.