And what really bites is when you damage a ship with that last eel. With the weather foul against you, no opportunity to use the deck gun to finish 'em off. Sometime later, she sinks, and even though still close by (within hydrophone range at least), you get NO CREDIT! Why, because the omnipotent AI has deemed that the weather did 'em in, not your torpedo blasting a bus sized hole in her hull.
I even trailed a group of three small coasties, running in line ahead off the New Jersey coast once in horrendous winter weather. Before I could overtake them and get into position, all 3 sank from the storm - their sad little wreck markings on the chart mocking me for the precious fuel I wasted trying to run them down.