No stick of dynamite thrown overboard to tell Ivan we see you?
There was a thread some time ago about Russian submarines in Swedish waters wherein some Freepers who were familiar with the practice of 'I see you' depth charging said that the common thing to do is toss a hand grenade wrapped in toilet paper over the side, to delay when the spoon flies and get some additional depth. No real danger to the submarine like a full-on depth charge would present, but it gets the point across.