I'm running latest IRAI among my mods list, and i just had a nice example of boats reaction and damages...
2 big troops transport following each other at 15 knots far south of Feroe islands. Aimed the first, and 3 torps later began to sink. Last torp was for the second one, nicely hitted too...
But the second one just slowed down and took some fire upstairs, tried to avoid me, and headed an other direction accelarating again.
Impossible to use the deck gun cause of waves, and as soon as i surfaced, machine guns illuminating sky!
So decided to follow him underwater, but his speed was still too fast.
Waited some time, and surfaced again to gain some speed.
I had to follow him for hours in the night before he finally sinked!
Fire was also gaining all the boat with time, and he lost gradually knots untill he stops and sunk
