It is in Stock also. According to the settings in the torpedo sim file, you will have a 0.5% chance of having a circle runner each time you shoot a torpedo. It's what sank the Wahoo and Tullibee and others that I cannot remember now... I have been playing the game since it came out, and I have probably had a good dozen circle runners over the years, and seemingly is more than a 0.5% chance...