I once saw 2 DDs (the only escort of a convoy) run into each other.
But they didn“t sink, they just got stuck there at 0kts.
Smartly i moved closer, put 1 impact torpedo into one of them. She exploded, taking down the other one with her...
But i only got credit for the 1 DD i hit
And it was on my first patrols, somehow the rest of the convoy disappeared while i was making my move to sink the escort...