I just started The Last Eagle by Michael Wenberg.
Forced into a neutral Estonian port for repairs during the chaos of the opening days of World War II, the Polish submarine, the "Eagle" and her crew are betrayed by their captain and captured by Nazi sympathizers. The crew, however, isn’t content to sit out the war. With help from unexpected sources—a naval attaché with the British Embassy and a courageous American reporter and her photographer sidekick—they overcome their captors, regain control of the "Eagle," and escape. The German’s are convinced the "Eagle's" crew has no stomach for a fight and will seek refuge in Sweden. But the Poles have something else in mind—join up with the British Fleet and continue fighting against their homeland's Nazi conquerors. They face stiff odds. The "Eagle" has little food and water, few torpedoes, and no sea charts. And before she can rendezvous with the British somewhere in the North Sea, she must traverse the Baltic, which has become little more than a Nazi-controlled lake.
This story is inspired by the exploits of the Polish submarine, "Orzel," during the early weeks of World War II.
Winston Churchill called her escape from the Nazis “an epic.”