Under the Hague Convention of 1907, section XIII, Article 12,[1] "belligerent ships" could enter a neutral port but were forbidden from remaining there for "more than twenty-four hours."

At the insistence of Germany, the Estonian military authorities boarded the ship, interned the crew, confiscated all the navigation aids and maps, and commenced removing all her armaments.

However, only fifteen of her twenty torpedoes were removed before the hoist cable parted; this was because it had been secretly sabotaged by her new commander, former chief officer, Lieutenant Jan Grudzinski.

Running half-submerged, Orzeł ran aground on a bar at the harbour mouth, where artillery fire damaged her wireless equipment.

Grudzinski managed to get the boat off the bar by blowing her tanks, and she proceeded out of the Gulf of Finland, intending to sail for a British port, the crew having heard a radio report that the Polish submarine Wilk had been welcomed in Britain.

The submarine's sole remaining navigational aid was a list of lighthouses, and using these as a reference, Orzeł followed a course along the Baltic coast, around Denmark, and out into the North Sea, where she came under attack by British as well as German forces, since without her wireless equipment she had no means of identifying herself.

[4] Rio de Janeiro was heading to Bergen in order to take part in the initial landings of Operation Weserübung – the invasion of Norway and opening move of the Norwegian Campaign.

On 1 and 2 June, radio messages were transmitted from the Rosyth Naval base ordering the boat to alter its patrol area and proceed to the Skagerrak (the strait separating Norway and Sweden from the Danish Jutland peninsula).

[6] Between 2008 and 2017 a number of Polish expeditions, both private and public-funded, searched the region of North Sea where she went missing with the hope of finding her final resting place.

In June 2013 the Polish Navy, following reports of a wreck of an unknown large submarine found in the North Sea, conducted one more expedition to check whether the ship could be Orzeł.