@febeling - quite true, and most effective at that! I believe schemes like these were deployed to some extent also in WWII, however the advent of sonar and, lat

@febeling - quite true, and most effective at that! I believe schemes like these were deployed to some extent also in WWII, however the advent of sonar and, later, radar probably made it less effective. It would still make life harder for the hunter, though - getting a good bearing/range/speed observation would definitely take longer, leaving the submarine vulnerable to detection for the duration.