Happens by accident, AFAIK error in torpedo gyro. Haven't seen it myself yet, running PE3+NSM. Might be something added by TMO or RFB, don't know for sure.
CollateralDamage; for info on sub classes, just search wiki.
for example Gato-class:
http://en.wikipedia.org/wiki/Gato_class_submarine
Sorry, don't know about the graphics thingy.