The movie suggests that the inking of Bauer's first submarine "Brandtaucher" was due to sabotage by the Brits. In real life it happened due to equipment failure as too much ballast-water was put inside. It is also believed that the submarine was not entirely completed and equipped due to monetary issues.
King Maximilian of Bavaria was around 40 when Bauer presented him his plans of the submarine. However he is portrayed as a 70-year old man.
While the submarine "Seeteufel" was indeed tested in Kronstadt, as shown in the movie, it was built in St. Petersburg not in Kronstadt.
In the movie Wilhelm Bauer got the idea of his submarine while being the artillery noncom. In real life it was when he was a member of the Bavarian army. After his ideas were refused he quit the Bavarian army and got hired as an artillery non-com at the Schleswig Army.
It is suggested that Wilhelm Bauer went to Kronstadt, Russia, straight from Munich. In real life he spent time in London, after being invited by Prince Albert. But after realizing that he didn't have all the opportunities he needed to build his submarines he used Russian support and went to Russia after the conflicts between Russia and BRitain.
The opening credits mention the blocking of the northern German border by the Danish army at the First Schleswig War and set it to 1849. This happened however in 1848.
In the first scene in Munich, set in 1851, there is a man shown riding a Draisine. While a Draisine as invented in 1818 it was not in use since 1822 after Drais left Germany for Brazil. In Germany this device was only built for children, not for adults and wasn't developed into a bicycle until the 1860s.