Continue through the side passage, with the barricade ships. Stay on the surface decks awash and keep an eye with the binoculars for any land battery or a patrol boat. 1/3 is OK; you dont want to make a big wake.
When you finish the passage, submerge. Continue with 1/3, checking the hudrophones towards the harbour. If there is no capital ships there, continue to the other side to get to the Atlantic. Near the enterance of the other (west) passage, sometimes there is an auxilliary cruiser. It's better than notning.
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