In peacetime, the US Navy is very careful about turning on it's active sonar because they're concerned about marine life. In wartime, though, that's all off. Other navies, other than maybe the Europeans and the Canadians, aren't so green.

Submarines don't use active sonar so much, but surface ships, being less concerned about stealth, use active sonar much more liberally. While a submarine is unlikely to go active unless maybe it'd already been shot at and still needed to find the target (even then, probably not), a surface ship might use active sonar as a search or screening sensor.

Not to mention the fact that most sub skippers probably wouldn't go near a harbor defended by four destroyers or FF's pinging away with helos and MPA's circling in the skies and friendly diesels lurking around.

It would be a major deterent. :|\

Some very old (fiction) books in my basement portray such things going on during world war II - though it's more by being told about it happening, or should I say happened, than then the reader taking part in the action.


DW Subs are particularly nasty for minelaying in enemy harbors, though.