You can sneak in past the blockade-ships, using this small entrance:
...but ALWAYS remember you have only 11m of water under kiel on periscope-depth!
I sneaked in during the night, after finding a small gap next to a wreck close to shore..I had only 3m tolerance on all 3 sides.
Then I had to wait stationary submerged all day, for evening to fall, and prepare for the attack at the Fiji-class that was lying on anchor, at 7000m West of my position...oxygen went down to 40%, but was quickly replenished in the 1st hr of dawn, after lying decks-awash for a little while.
There was a guy fishing closeby, but he never noticed us lol.
The thunderstorm overhead made it all pretty creepy.
I fired 2 electric torps, set at 6.1m (Fiji=5m draft) on a 1degr. spread, from 1200m.
They never knew where it was coming from, and the (10ktons) Fiji sank within 2hrs.
I escaped the same way I came from, on silent running, with plenty of oxygen and E-power.
By the time that other ships came investigating, we were already gone, back through the barricade.
Once beyond that barrier, there's no way they can get us anymore, unless they send airplanes.
Well...let them come!
Sailing from Bergen in typeVIIC fully upgraded, June '42, GWX.