'Worek' was a Polish naval operation in the first days of World War II for its five submarines to form a screen to prevent German naval forces from effecting landings on the Polish coast, and to attack German warships bombarding Polish coastal fortifications, in particular the fortifications of the Hel peninsula covering the approaches to Danzig (1 September/14 October 1939).

The operation achieved nothing as the Germans had no plans for naval landings. The operation required the submarines to operate in a confined area in shallow coastal waters, which rendered the five boats vulnerable to the German anti-submarine forces. As a result, despite making a number of attack attempts, the submarines were unable to sink any German ships during the operation, although a mine placed by Żbik did sink a German minesweeper. No Polish submarines were lost to German action, but the boats suffered typical wear and an increasing number of technical problems, forcing the termination of the operation by mid-September.

The plan had been created for the submarines Orzeł, Wilk, Sęp, Żbik and Ryś for implementation in the event that superior German surface forces gained the upper hand in the Baltic Sea from a Polish navy whose only significant surface assets were four destroyers and some minelayers. The submarines were to operate near the Polish coast, in the area of the Bay of Gdańsk and the Hel peninsula, where they were to engage German ships shelling the Polish coast or attempting to land forces on it. The plan explicitly stated that the submarines were to act according to international law, and therefore single unarmed ships had to be warned before being attacked.

Orzeł was to take the position farthest inside Gdańsk Bay, from Jastarnia to the estuary of the Vistula river. To the east of Orzeł, in the entry to the bay, was Wilk. The remaining three submarines were to operate in the area to the north of the Bay of Gdańsk: Sęp was farthest to the west near Rozewie, Ryś was farthest to the east, and Żbik in the middle. The boats had separate areas for battery charging during the night: Orzeł even deeper within the Bay of Gdańsk, and the other boats to the north of their operational positions.

'Worek' was implemented on the start of the German 'Weiss' (i) invasion of Poland when, several hours after the beginning of hostilities, the boats received the implementation order, and had departed to reach their operational areas by the end of the day. All the boats tried to engage German ships, but all failed. The German forces had numerical superiority and were ably supported by the Luftwaffe. Although the boats were frequently depth-charged, none was destroyed. Eventually, after a series of failed attacks, the Polish skippers decided to call off their efforts. Orzeł abandoned her sector on 4 September and on 15 September docked in the Estonian port of Tallinn for rest and repairs (international law allowed 24 hours before the ship had to be interned). The boat was seaworthy and, after a failed Estonian attempt to take control of her, escaped to reach the UK by 14 October. The boat was sunk in 1940. Damaged and unable to engage Germans units, Ryś was eventually interned in a Swedish port from 17 September. Sęp was badly damaged by a German destroyer on 2 September, abandoned the operation two days later and headed to Sweden, where it and its crew were interned from 17 September. Wilk was the first Polish submarine to reach the UK: unlike that of Orzeł, the boat’s captain decided not to dock at a continental port and risk internment, but to head straight for the UK, where his boat arrived on 20 September. The boat survived the war. Żbik was the only Polish submarine to succeed in sinking a German vessel when, on 10 September the minefield it had laid sunk the minesweeper M 85. Increasingly damaged and low on provisions, the boat was interned in a Swedish port from 25 September.