You need to check out Gibraltar in April 1940. You can run below the layer (160m or deeper) to the Rock of Gibraltar then creep into the harbour area. HMS Nelson (33k tons) and a small depot ship (6500 tons) on the north western side and three Southampton/London class (10-13k tons each) on the north eastern side along with three static destroyers. In the harbour itself there's another Southampton class plus a troop transporter, modern tanker, large and medium cargo and a few other small ships. Watch out for torpedo nets on the northern side of the harbour - I took a lot of damage when I hit one net and broke the surface for a few seconds as those capital ships have a shedload of firepower (but can't traverse very quickly). Torpedo nets in general seem to finish about 2 submarine widths from the harbour walls in any port, so I sneak in by running
very close to the harbour walls.
The only things protecting Gib are the static surface ship's guns and 2 or 3 ASW trawlers and Isles class, all of which seem to be either blind and deaf or just stupid. Ran out of internals in the IXB and have had to extract to reload externals and go back in.
If the protection is as dopey as it was last time, I'll easily clear 100k tons and get away with my boat intact.