With three other minesweepers, we ...
... did surveillance work in the Baltic sea, in internatianal waters, between Fehmarn Island and Rostock.
That meant: 24 hours shipping very slowly up and down, the 24 hours duty as a "piquet boat" (that originally means 'behind the enemy lines' - here it was usually just outside the 3-mile-border).
My duty was to photgraph etc any ship from the east nations.
The GDR navy did the same, but mostly anchored
They changed the boat at duty at night. So we, as piquet boat, had to go close to the GDR boat (hand weapons and gun ready), get the number and ... hope that no-one started the third world war
One night, we (slightly! officially of course not) were inside the 3-mile-zone because we had to catch a "foreign person", who was very exhausted, out of the water.