[Corsair]

One important thing for detection is the engines revs. Ideally you don't want more than 100 rpms (gauges in the command room and conning tower) so you switch your engine control dial to speed display and slow down until you get the desired revs. 1 knot is fine. Depending on what game you play at that speed your sub will either maintain depth (stock game) slowly rise (GWX) or slowly sink (NYGM).