I recently had two DD's circling me ... unfortunately for them, one was circling clockwise while the other was going counter-clockwise. Yup... you can see where I'm going with this.
They clipped each other and one went down as a result the other seemed unaffected.
I did not get credit for it... but it was on account of me that the ship was sunk technically, so I told my boys to stitch another tin can on the kill flag anyways.