AFAIR it`s only passive with no 'send' option.
As for using the sonar - I`ve made few missions recently with GWX 1.03 and XXI with Nibelung. The sonar is great for lone merchs as they can`t notice your pings anyway
The problem is,the sonar is not always precise. Besides, I tried to use it on a convoy and it was extremely hard because of multiple targets with VERY similiar bearings - the sonar did estimate range for different targets and therefore it was impossible to estimate range accurately
Perhaps it`s just me and I`m doing it not very well.