I remember my first friendly fire incident.
I was well into the St. Georges Canal patrolling about looking for some merchants at the choke point on a particularly unproductive patrol.
Then in the night on the horizon i spotted 3 destroyers traveling in column from West to East.
These guys were moving along at about 5kts... looked sneaky, looked like they were up to something.
I plotted a solution and let 3 fish go at them.
first ship in the column missed astern.
second ship in the column - dud torpedo.
third ship in the column direct hit.
she never sunk, but slowed to about 2 knots and her decks were nearly awash as the deck was now more or less the water line
i closed the range when the other two destroyers left the area and peered through the scope to check on the sinking progress and line up a shot to finish her off.
while inputting my solition - i saw the flag - she was a german ship.
But why were they so deep into enemy home waters... i mean we were 30KM off shore!! well into the St. Georges Canal!
not wanting to be pegged with her sinking, i left the area at high speed while she was still afloat.
Lesson learned: always check the flags, and when in doubt - hold your fire