How do I use the sonar visualisation in submarines mode?

Issue is, I know that in Battle of the Atlantic event, when playing as Defending Team (USA), while playing USS Fletcher, you shuld see a blue outline of UBoot when it’s pinged close to you. Yet I have played about 20 matches as USA, both as Tacoma and Fletcher, and I have never seen it, in result playing completely on my lucky aim and predictions. Is it an option I need to turn on or is it just a bug?

It is a very faint outline…perhaps you missed it?
It is one of those things that you can barely see in the battle confusion (shots, weather, torpedos, friendlies, etc…), but once you know what you are looking for it becomes easier to spot…
I seen it every game once i get close to the targets…you see red points in map, you go there :)

Also…i reduce speed a bit when getting close to target…IRL it would improve sonar performance, but not even sure if modelled in game…i try anyway…
(dont get too slow…contrary to RL, submarines will fire at destroyers A LOT)