Well, it seems to be random at times, but in the case of troop transports it may or may not depend on the ship's destination and origin. Case in point, a speeding 18-knot European liner that I snagged on my first patrol in my new Gato spawned this:
Whereas the next liner that I sunk afterwards had zero survivors:
In the first case, I'm glad to see that I did my job right. Looks like those troops will be swimming home
